Mushroom & Caramelized Onion Quiche

Mushroom & Caramelized Onion Quiche

Meet your new brunch star: mushroom & caramelized onion quiche with gruyere.  All-butter, flaky pie crust filled and baked with eggs, half and half, sautéed mushrooms, caramelized onions, gruyere and fresh thyme.


This quiche is among my very favorites, featuring sautéed mushrooms, sweet caramelized onions, and rich gruyere cheese, all enhanced with a hint of fresh thyme. Perfect for any time of day, from a sophisticated brunch to a cozy dinner, this quiche promises to be a crowd-pleaser at any gathering.

Mushroom & Caramelized Onion Quiche

THE FILLING

Using the same custard ratio as this Denver quiche and this ham and asparagus quiche, I’ve added earthy mushrooms, perfectly caramelized onions, plus shredded gruyere cheese for an absolutely delicious quiche combination.  For the egg custard ratio to be silky and have a just-right richness, I beat four large eggs and fill a 2-cup liquid measuring cup to the 2 cup mark with half and half. It ends up being about 1.5 cups of half and half, depending on the liquid volume of the eggs.  This half & half and egg formula guarantees a silky, but not too rich custard, and is courtesy of Julia Child in her book, The Way to Cook. (I discovered this ratio when embarking on a journey to nail this deep-dish spinach quiche a few years ago.)

THE CRUST

Nothing compares in flavor to that of an all-butter crust.  A base of homemade all-butter crust transforms any quiche from good to great, but especially this mushroom quiche recipe!  You won’t believe how easy it is to make a homemade pie crust, especially if you own a food processor.  Best part: it can be made ahead and refrigerated or frozen until it’s time to assemble the quiche.

My recipe for an all-butter pie crust, aka pâte brisée, is one I learned while taking pastry classes. You can also use a store-bought pie crust if you’re short on time!  In either case, we’re blind baking the pastry before adding the filling ingredients to avoid a soggy crust bottom. Don’t skip this step. See this tutorial for more guidance on blind baking a pie crust.

INGREDIENT & SUBSTITION NOTES

  • 1 Recipe all-butter pie dough (see below), or store-bought pie crust
  • Eggs – four large eggs
  • Half and half – Or use half heavy cream and half milk. The half and half lends richness to the egg custard. 
  • Mushrooms – baby bella, cremini or even button mushrooms all work! Trim the ends and slice before you begin cooking. Browning the mushrooms before adding them to the filling is key as they’re more flavorful.
  • Large yellow onion –  The onion will cook down considerably as it caramelizes!
  • Gruyère cheese – We’re using 1 cup of shredded gruyere in this recipe.  Gruyere adds a nutty richness to the quiche.  Feel free to substitute another cheese in its place, like fontina, Swiss or cheddar cheese, but keep in mind you may have to adjust the salt. 
  • Salt & pepper – A modest amount of salt since we’re using ham, and a couple of generous turns of freshly ground black pepper add the right balance of seasoning.  You’ll season with salt and pepper as you 
  • Fresh thyme – Thyme adds a savory profile to the quiche and goes so well with the flavor of the caramelized onions and the mushrooms. If you’re substituting dried thyme, reduce to 1/2 teaspoon.
Mushroom & Caramelized Onion Quiche ingredients

HOW TO MAKE MUSHROOM & ONION QUICHE

1. MAKE THE ALL-BUTTER PIE DOUGH

Making homemade pastry is easier than you think.  This all-butter recipe is delicious and takes your quiche to the next level!  (If you’re using store-bought quiche crust, skip to step 2.)

  • Add flour and salt to a food processor and pulse 2-3 times to combine. 
  • Add butter and pulse 5-6 times, until butter begins to break up and is about the size of walnuts. 
  • Slowly add lemon juice(vinegar)/water combination through pour spout while pulsing.  You want the dough to look a little dry but it should be wet enough to hold shape between two fingers when you press it.  I tend to use all of the water in my dry, Colorado kitchen, but you may not need all the water/lemon juice mixture!
  • Dump slightly crumbly dough onto piece of plastic/silicon wrap and pull corners of wrap around dough, pushing dough together until you can form a 6-inch disk.  Wrap tightly and refrigerate for at least 30 minutes or up to 24 hours, until firm. (The disk can also be frozen at this point.)

2. ROLL & FORM THE CRUST

  • Remove prepared pie dough “disk” from refrigerator and let it sit on the counter until it’s soft enough to roll out, but still cold.  If dough has been in freezer, let it thaw in fridge overnight and place on counter to soften for an additional 10-15 minutes. 
  • Roll out the disc of dough on floured counter into roughly a 12-inch circle.  For more detail on how to roll out, see my how to: roll out pie crust tutorial.
  • Roll dough up around rolling pin loosely, and gently center it in 9-inch pie plate.
  • Press dough firmly into corners and up the sides of pan.  Trim dough around the top, with up to 1 inch of overhang.  Use extra dough to patch any holes or cracks. 
  • Chill prepared dough in fridge while you prepare filling and heat oven to blind-bake.

3. BLIND BAKE THE CRUST AND MAKE THE FILLING

  • Preheat oven to 375 degrees. This will be the temperature at which you’ll blind bake the crust and bake the quiche.
  • Prepare the filling: In a large liquid measuring cup (or medium bowl), whisk four large eggs. Add just enough half and half to reach 2 liquid cups (will be about 1.5 cups of half and half). Set aside.
make quiche custard
  • Prepare fresh thyme: Hold thyme stalk at the top and then firmly run the thumb and forefinger of your other hand along the stalk from top to bottom, breaking off the leaves as you go. Run your knife through the leaves to chop them a little.  Set aside 2 teaspoons.  
  • Sauté vegetables: In large skillet, saute onions over medium heat for about 5 minutes, until they’re just beginning to brown.  Turn heat down to medium-low and continue cooking another 25-35 minutes, stirring occasionally, until golden brown and cooked down considerably.  Remove to cool on a plate.  Add remaining 1 tablespoon of olive oil and cook mushrooms over medium heat for about 5 minutes until they begin to release most of their liquid.  Add fresh thyme and salt/pepper to taste and continue cooking until well browned.  Set aside to cool with the caramelized onions while you blind bake your crust.
raw onions in skillet
caramelized onions

raw mushrooms in a skillet
browned mushrooms
  • Line pastry with parchment paper or aluminum foil and fill with pie weights or dried beans. Bake in middle of the oven for 15 minutes. Remove from oven and remove pie weights and parchment/foil. Prick pastry all along the bottom with a fork and bake for another 8-10 minutes, until just beginning to brown. Remove from oven onto cooling rack.
blind bake pie crust

4. BAKE QUICHE

  • Add sautéed mushrooms and caramelized onions to the blind-baked crust, and sprinkle shredded gruyere on top of mushrooms and onions.  Finally, carefully pour the the egg mixture right on top of the vegetables and cheese.  
  • Place quiche on rimmed baking sheet. Bake for 40-45 minutes, until golden brown and puffed slightly and center of the quiche is just about set. Cover crust with pie shields if it begins to brown too much, or use thin strips of foil.

5. COOL & SERVE

  • Allow to cool on a cooling rack for at least 15 minutes (or serve at room temperature). 
  • Slice into eight slices.  I find it works best to remove entire (slightly cooled) quiche onto a cutting board and gently saw back and forth with a serrated knife, first in half, and then in half the other way.  Finally, slice each quarter in half.  This will give you eight even slices. 
  • Garnish with more fresh thyme, if desired and serve with a green salad or fresh fruit.
Mushroom & Caramelized Onion Quiche
Mushroom & Caramelized Onion Quiche

FREEZING & STORAGE INSTRUCTIONS

  • Leftover quiche can be stored in the refrigerator for 3-4 days, sealed in a glass lock container. 
  • To make ahead, prepare filling ingredients and store in the refrigerator. Prepare pie crust and place disk in refrigerator (or freezer, for longer) for up to 24 hours. Blind bake and assemble according to recipe.
  • To freeze quiche, wrap completely cooled quiche in several layers of foil. To reheat, set frozen quiche in cold oven and heat to 350 degrees for about 25 minutes, or until hot throughout.

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Mushroom & Caramelized Onion Quiche

All-butter, flaky pie crust filled and baked with eggs, half and half, sautéed mushrooms, caramelized onions, and gruyere and fresh thyme.
Prep Time1 hour
Cook Time40 minutes
Course: Breakfast, brunch
Keyword: mushroom and onion quiche
Servings: 8

Ingredients

  • 1 all-butter pie dough (see below), or store-bought pie crust
  • 4 large eggs
  • 1 1/2 cups half and half
  • 8 oz mushrooms baby Bella or cremini or button mushrooms are all good
  • 1 large onion
  • 1 cup gruyere shredded (3 oz)
  • 1/2 tsp freshly ground pepper
  • 1/2 tsp kosher salt
  • 2 tsp fresh thyme or use 1/2 teaspoon of dried thyme

Instructions

  • MAKE THE ALL-BUTTER PIE DOUGH: (If you’re using store-bought crust, skip to step 2.)
    Add flour and salt to a food processor and pulse 2-3 times to combine. Add butter and pulse 5-6 times, until butter begins to break up and is about the size of walnuts. Slowly add lemon juice(vinegar)/water combination through pour spout while pulsing.  You want the dough to look a little dry but it should be wet enough to hold shape between two fingers when you press it.  I tend to use all of the water in my dry, Colorado kitchen, but you may not need all the water/lemon juice mixture!Dump slightly crumbly dough onto piece of plastic/silicon wrap and pull corners of wrap around dough, pushing dough together until you can form a 6-inch disk.  Wrap tightly and refrigerate for at least 30 minutes or up to 24 hours, until firm. (The disk can also be frozen at this point.)
  • ROLL & FORM THE CRUST:
    Remove prepared pie dough “disk” from refrigerator and let it sit on the counter until it’s soft enough to roll out, but still cold.  If dough has been in freezer, let it thaw in fridge overnight and place on counter to soften for an additional 10-15 minutes. 
    Roll out the disc of dough on floured counter into roughly a 12-inch circle.  For more detail on how to roll out, see my how to: roll out pie crust tutorial.
    Roll dough up around rolling pin loosely, and gently center it in 9-inch pie plate.
    Press dough firmly into corners and up the sides of pan.  Trim dough around the top, with up to 1 inch of overhang.  Use extra dough to patch any holes or cracks. 
    Chill prepared dough in fridge while you prepare filling and heat oven to blind-bake.
  • BLIND BAKE THE CRUST AND MAKE THE FILLING:
    Preheat oven to 375 degrees. This will be the temperature at which you’ll blind bake the crust and bake the quiche.Prepare the filling: In a large liquid measuring cup (or medium bowl), whisk four large eggs. Add just enough half and half to reach 2 liquid cups (will be about 1.5 cups of half and half). Set aside.
    Prepare fresh thyme: Hold thyme stalk at the top and then firmly run the thumb and forefinger of your other hand along the stalk from top to bottom, breaking off the leaves as you go. Run your knife through the leaves to chop them a little.  Set aside 2 teaspoons.  
    Saute vegetables: Saute onions over medium heat for about 5 minutes, until they're just beginning to brown.  Turn heat down to medium-low and continue cooking another 25-35 minutes, stirring occasionally, until golden brown and cooked down considerably.  Remove to cool on a plate.  Add remaining 1 tablespoon of olive oil and cook mushrooms over medium heat for about 5 minutes until they begin to release most of their liquid.  Add fresh thyme and salt/pepper to taste and continue cooking until well browned.  Set aside to cool with the caramelized onions while you blind bake your crust.
    Line pastry with parchment paper or foil and fill with pie weights. Bake in middle of the oven for 15 minutes. Remove from oven and remove pie weights and parchment/foil. Prick pastry all along the bottom with a fork and bake for another 8-10 minutes, until just beginning to brown. Remove from oven onto cooling rack.
  • BAKE QUICHE:
    Add sautéed mushrooms and caramelized onions to the blind-baked crust, followed by the shredded gruyere cheese.  Finally, carefully pour the the egg mixture right on top of the vegetables and cheese.  
    Place quiche on rimmed baking sheet. Bake for 40-45 minutes, until golden brown and puffed slightly and center of the quiche is just about set. Cover crust with pie shields if it begins to brown too much, or use thin strips of foil.
  • COOL & SERVE:
    Allow to cool on a cooling rack for at least 15 minutes (or serve at room temperature). 
    Slice into eight slices.  I find it works best to remove entire (slightly cooled) quiche onto a cutting board and gently saw back and forth with a serrated knife, first in half, and then in half the other way.  Finally, slice each quarter in half.  This will give you eight even slices. 
    Garnish with more fresh thyme, if desired and serve with a green salad or fresh fruit.


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