Flaky Quiche with Caramelized Onions and Sauteed Mushrooms

Caramelized Onion and Sautéed Mushroom Quiche makes an elegant breakfast or brunch centerpiece and is equally satisfying for lunch or dinner.

This versatile quiche—rich caramelized onions, deeply browned mushrooms and a silky egg custard topped with creamy goat cheese—works any time of day. It’s a great recipe to make for a leisurely weekend brunch, a holiday breakfast, or a simple weeknight dinner served with a salad. The flavors are familiar yet elevated, and the quiche keeps well for leftovers.

I hadn’t made quiche until recently, but after trying a crustless vegetable version at a friend’s house, I decided to add a buttery crust for extra texture. The idea came together from memories of appetizer tarts made in a cooking class long ago: the same combination of sweet onions, savory mushrooms and tangy goat cheese works beautifully in a full-size quiche.

For convenience I used a rolled, store-bought pie crust, but you can substitute puff pastry, phyllo layers, or a homemade crust if you prefer. If you want fewer carbs or a gluten-free option, make the quiche crustless—simply oil the baking dish and pour the filling directly into it.

How to make Caramelized Onion and Sautéed Mushroom Quiche

Start by preparing the caramelized onions and sautéed mushrooms. Caramelizing onions takes time and can’t be rushed; patience pays off with deep, sweet flavor. If you prefer a hands-off approach, make a large batch of caramelized onions ahead of time and refrigerate or freeze the remainder for future use. You only need a portion of that batch for this quiche.

Mushrooms should be cooked until their liquid has evaporated and they develop a good brown color. Season them lightly with thyme, salt and pepper. Both the onions and mushrooms can be made a day in advance and stored in airtight containers to save time on the day you bake the quiche.

To finish the filling, whisk eggs and whole milk until blended. Layer the caramelized onions and mushrooms in a prepared crust, pour over the egg mixture, then scatter crumbled goat cheese across the top. Bake until the custard is set but still slightly jiggly in the center; it will continue to firm as it cools.

Ingredients

• 1 tablespoon unsalted butter
• 1 large yellow onion, thinly sliced
• 1 tablespoon olive oil
• 16 ounces mushrooms (white or brown, sliced) — you can use cremini, portobello slices, or a mixed medley
• 1/4 teaspoon dried thyme (or 1 teaspoon fresh, minced)
• Salt and pepper to taste
• 4 large eggs
• 1 cup whole milk
• 1 rolled pie crust (store-bought or homemade; look for the rolled type rather than one already in a disposable dish)
• 4 ounces goat cheese, crumbled (about 1/2 cup)

Equipment and baking notes

A 9-inch pie plate, quiche dish, fluted tart pan with removable bottom, round cake pan or springform pan will work. A fluted tart pan with removable bottom makes unmolding easier, but it is not required. Preheat the oven to 375°F (190°C) before baking.

Method

1. Melt the butter in a 10–12″ skillet over medium heat. Add the sliced onions and cook, stirring often, until they are very soft and a deep golden brown. Reduce the heat if they brown too quickly and add a tablespoon of water at a time if needed. Caramelizing can take 30 minutes or longer. Transfer the onions to a bowl when finished.
2. Return the empty skillet to medium heat, add the olive oil, then add the mushrooms. Cook until the mushrooms are browned and their liquid has evaporated. Stir in thyme and season with salt and pepper. Remove from heat and set aside.
3. Preheat oven to 375°F. In a medium bowl, whisk together the eggs and milk until combined.
4. Roll out the pie crust and fit it into a 9-inch pie plate or quiche dish. Spread the caramelized onions and sautéed mushrooms evenly over the crust. Pour the egg mixture over the vegetables and sprinkle the crumbled goat cheese on top.
5. Bake for 30–40 minutes, until the egg custard is set and the top is lightly golden. Let the quiche rest for 10–15 minutes before slicing to make clean slices.

Serving suggestions

Serve warm or at room temperature with a crisp green salad, fresh fruit, or roasted vegetables. This quiche is a welcome addition to holiday brunches and potlucks, and leftovers reheat well in a low oven or air fryer for a quick meal the next day.

Make-ahead and storage

Onions and mushrooms can be prepared ahead and refrigerated in airtight containers for up to one day. The assembled quiche can be baked and then refrigerated for up to three days. Reheat slices in a 325°F oven until warmed through, or enjoy cold.

Nutrition and adaptations

For a lower-carb or gluten-free version, omit the crust and bake the filling in a well-oiled pie plate. A crustless quiche reduces carbohydrates and calories while keeping the same savory flavor. You can also swap milk for a lighter dairy or nondairy alternative, and use reduced-fat cheese to lower total fat.

This Caramelized Onion and Sautéed Mushroom Quiche is easy to adapt and always impressive on the table. Enjoy it any time you want a comforting, flavorful meal that travels well from breakfast to dinner.