Caramelized Onion and Mushroom Quiche
What I love about Caramelized Onion and Mushroom Quiche
This Caramelized Onion and Mushroom Quiche has become one of my absolute favourite dishes to meal prep for the week. For starters, it’s hearty, wholesome, and packed with rich, satisfying flavour. From the sweet, slow-cooked onions and earthy shiitake mushrooms to the nutty Emmental cheese and fragrant fresh thyme, every bite is beautifully balanced.
Really though, I truly love a good quiche—not just for breakfast, but also as a quick, easy lunch or even a mid-afternoon snack when hunger hits early. Thanks to its high protein content, it’s incredibly filling and helps keep you satisfied throughout the day.
Even better, this quiche makes 8 generous slices, so you’ll have a nutritious, delicious option ready to go all week long. Whether you’re planning ahead or just want something you can grab and reheat, this recipe is a total win. And if you like this recipe, be sure to check out my recipe for Potato Crusted Ham and Swiss Quiche, another favourite!
Recipe Notes
A few things to keep in mind:
Here’s a list of ingredients that you will need:
- High-quality eggs – First of all, try to find organic pasture-raised eggs for the richest yolks and best health benefits. You will need 8 eggs for this quiche
- Onion – You can use yellow onion, white onion or even shallots for this recipe. All will work.
- Mushrooms – Additionally, you will need some shiitake mushrooms for this recipe. I try to avoid white and brown mushrooms, which are lacking in flavour, and go for something more unique or some type of a chef’s blend.
- Prepared quiche crust – Any quiche crust will work as long as it’s a 9″ deep dish. Or, you can even make it crustless!
- Thyme – Do use fresh thyme if you can. The flavour is so delicious with the mushrooms and onions. Dried thyme could work in a pinch but fresh is always best!
- Emmental cheese – Finally, Emmental, a delicious and authentic Swiss cheese, makes this quiche what it is! You can find it in the specialty cheese section at most grocery stores.
How to Make it
Step 1: Caramelize the mushrooms and onions.
In a medium-sized cast iron or stainless steel pan, add the butter and melt over low-medium heat. Add the sliced onions and mushrooms and cook, stirring every few minutes until golden brown and caramelized, about 10-15 minutes. Season with salt and pepper.
Step 2: Whisk the egg mixture.
In a small bowl, whisk the eggs, cream, thyme, salt and pepper until combined. Stir in the Emmental cheese. Set aside.
Step 3: Add onions and mushrooms to prepared quiche crust.
Add the caramelized onions and mushrooms to the bottom of the prepared quiche crust in an even layer.
Step 4: Add the egg mixture into the quiche crust.
Pour the egg mixture on top of the onions and mushrooms in the prepared quiche crust and gently stir with a fork to lift the onions and mushrooms slightly.
Step 5: Bake the quiche.
In the preheated oven, bake the quiche on the middle rack for 20-25 minutes or until golden brown on top and it no longer jiggles in the centre. Let cool at least 10 minutes before slicing. Enjoy with fresh bread and a side salad for brunch.
FAQ
Yes! You absolutely can make it crustless. You will still need a 9″ pie dish. Make sure you butter it extremely well before adding the egg mixture so it doesn’t stick.
I find Swiss Emmental works best with the other ingredients, but parmigiana cheese, gruyere or regular Swiss cheese will work as well and also add delicious flavour. If you want a lower-budget option, then go for a sharp white cheddar cheese.
Yes, you can definitely use milk instead of cream. If going this route, I recommend using whole milk.
I recommend storing any leftovers in an airtight container in the fridge for up to 1 week. Reheat in the oven at 350F for 10 minutes or until warmed through for best results.
Caramelized Onion and Mushroom Quiche
Equipment
- 1 9" Pie or Tart Deep Dish
- 1 Medium-sized Cast Iron or Stainless Steel Skillet
Ingredients
- 4 tablespoons unsalted butter for cooking
- 1 white onion thinly sliced
- 3 cups shiitake mushrooms thinly sliced
- 1 9" prepared quiche crust (or 9" pie dish for crustless)
- 8 organic free-range eggs
- 1/2 cup organic heavy cream
- 5-7 sprigs fresh thyme (leaves removed)
- 2 teaspoons sea salt
- 1 teaspoon black pepper
- 3/4 cup shredded Swiss Emmental cheese
Instructions
- Preheat the oven to 400F.
- Heat a cast iron pan or skillet over low-medium heat and add the butter.
- Once the butter has started to melt, add the sliced onions and mushrooms and sauté until the onions are caramelized and the mushrooms are browned.
- In a medium-sized bowl, add the eggs, cream, thyme, salt and pepper and whisk until smooth. Add the cheese and whisk in to mix.
- *Add the mushrooms and onions to the bottom of the quiche crust (or pie dish for crustless) and then pour the egg mixture over top.
- Bake for 20-23 minutes or until golden brown on top and no longer jiggling. Let cool before cutting into slices.
- Enjoy!
Notes
- High-quality eggs – Try to find organic pasture-raised eggs for the richest yolks and best health benefits.
- Onion – You can use yellow onion, white onion or even shallots for this recipe.
- Mushrooms – Try to avoid white and brown mushrooms, which are lacking in flavour, and go for something more unique or some type of a chef’s blend, if not shiitake.
- Prepared quiche crust – Any quiche crust will work as long as it’s a 9″ deep dish. Or, you can even make it crustless!
- Thyme – Do use fresh thyme if you can. The flavour is so delicious with the mushrooms and onions. Dried thyme could work in a pinch but fresh is always best!
- Emmental cheese – Finally, Emmental, a delicious and authentic Swiss cheese, makes this quiche what it is! You can find it in the specialty cheese section at most grocery stores.
