These little mini quiches are perfect to bring to a brunch and they’re really not that hard to make. I made these the night before for my friend’s baby shower and they reheated perfectly the next day. A crispy mashed potato shell pressed into a cupcake tin and pre-baked until golden, filled with buttery leeks, sautéed mushrooms, and a silky smooth egg custard, then topped with Gruyère and baked until set and golden. Super quick and easy because no pastry dough, just mashed potato for the crust!

Why You’ll Love This Recipe

• Potato crust instead of pastry — crispy on the outside, soft inside. I honestly think it’s better than a traditional shortcrust pastry in terms of flavor in my opinion!!
• Slow cooked leeks — low and slow until tender and sweet, they’re one of the best fillings for a quiche
• Silky smooth custard — strained through a sieve so it’s perfectly smooth
• Gruyère on top — because there’s no better cheese for a quiche

Potato Crust Mushroom Leek Quiche: No Stress Brunch Dish

A potato crust solves all of the time and stress that comes with making a traditional quiche crust. Mashed russet potato pressed into a cupcake tin and baked until the edges are lightly golden gives you something crispier and more flavorful than most pastry crusts and it comes together in a fraction of the time. The filling is a combination of two of the best quiche fillings in the world, slow-cooked sweet leeks and deeply savory sautéed mushrooms. The custard is classic French style with a high cream-to-milk ratio that sets silky and rich. These are the kind of thing you bring to a potluck and everyone asks for the recipe before they’ve even finished eating.

Potato Crust Mushroom Leek Quiche Ingredients

POTATO CRUST

• 800 g russet potatoes, peeled and chopped into 1 inch pieces
• Salt, for the boiling water
• Oil spray, for the cupcake tin

MUSHROOM FILLING

• 250 g mushrooms, thinly sliced
• 1 tbsp butter
• ½ tsp fresh thyme
• Pinch of salt

LEEK FILLING

• 180 g leeks, cleaned, split lengthwise and thinly sliced crosswise
• 1 tbsp butter
• Pinch of salt

CUSTARD

• 3 large eggs
• 3 large egg yolks
• 300 g heavy cream
• 150 g whole milk
• ½ tsp salt

TOPPING

• Gruyère cheese, freshly shredded
• Fresh chives, chopped

The Potato Crust

The potato goes in heavily salted boiling water, gets cooked until completely fork tender, drained thoroughly, and mashed until smooth. The mashed potato then gets pressed into the cupcake tin and baked until the edges turn lightly golden. The pre-bake is important! It sets the crust and gives you a firm shell that won’t go soggy when the custard goes in.

Use a shot glass or any small object with a diameter slightly smaller than your cupcake tin cavities to press the potato into a cup shape. Press firmly and evenly so the walls are a consistent thickness and won’t collapse.

The Mushrooms

I found the best way to cook mushrooms is in a dry hot pan with no butter, no oil, and cooked down until all the water they release has completely evaporated. Mushrooms are mostly water and if you skip this step that water ends up in your quiche filling and dilutes the custard. Once the water is gone and the mushrooms start to take on color you add the butter, thyme, and salt.

The Leeks

Low and slow is the best way to cook leeks. A tablespoon of butter, a pinch of salt, and a lid on the pan over low heat for 15-20 minutes, stirring every few minutes, until they’re completely tender, sweet, and slightly silky. Don’t rush this on high heat!

The Custard

Classic quiche custard with eggs, egg yolks, heavy cream, whole milk, and salt. The additional egg yolks compared to whole eggs give you extra richness and a more tender silky set. The ratio of cream to milk here is weighted toward cream which gives you a custard that’s luxurious rather than thin. Running it through a sieve once before pouring helps to break up any stringy egg bits and gives you a completely smooth, uniform custard that sets beautifully.

How To Make Potato Crust Mushroom Leek Quiche

COOK THE MUSHROOMS

1. Dry sauté: Heat a pan over medium-high heat until hot. Add the thinly sliced mushrooms directly to the dry pan with no butter or oil. Cook stirring occasionally until all the water has completely evaporated and the mushrooms start to take on color.
2. Add butter and season: Add butter, fresh thyme, and a pinch of salt. Stir until the mushrooms are well coated and slightly golden. Remove from heat and set aside.

COOK THE LEEKS

3. Slow cook: In a pan over low heat melt butter. Add sliced leeks and a pinch of salt and stir to combine. Cover with a lid and cook on low for 15-20 minutes stirring every few minutes until the leeks are completely tender, sweet, and slightly silky. Remove from heat and set aside.

MAKE THE POTATO CRUST

4. Boil potatoes: Place peeled and chopped russet potatoes in a pot of heavily salted cold water. Bring to a boil and cook until completely fork tender. Drain thoroughly and let steam dry for a few minutes.
5. Mash: Mash the potatoes until completely smooth. Season with salt to taste.
6. Pre-bake the shells: Preheat oven to 350°F. Spray a cupcake tin generously with oil. Evenly distribute the mashed potato into the 10 cupcake cavities. Use a shot glass or small object with a diameter slightly smaller than the cavity to press the potato firmly into a cup shape with even walls. Bake for about 15 minutes until the edges are lightly golden brown. Remove from oven.

MAKE THE CUSTARD

7. Whisk: In a bowl whisk together eggs, egg yolks, heavy cream, whole milk, and salt until fully combined. Run through a fine mesh sieve for an extra smooth custard.

ASSEMBLE AND BAKE

8. Fill: Into each pre-baked potato cup add a spoonful of mushrooms and a spoonful of leeks. Pour the custard mixture over the fillings until each cup is just about full. Top generously with freshly shredded Gruyère.
9. Bake: Bake at 350°F for about 20 minutes until the tops are golden brown and the custard is set with just a very slight wobble in the center.
10. Finish and serve: Let cool for a few minutes before removing from the tin. Top with fresh chopped chives and serve warm.

Storage & Reheating

Storage
Store cooled quiches in an airtight container in the fridge for up to 3 days.

Reheating

• Oven (best method): Reheat at 325°F for 8-10 minutes until warmed through and the potato crust crisps back up
• Air fryer: 325°F for 5-6 minutes for a crispy result
• Microwave: Works in a pinch but the potato crust will soften. Heat in 30-45 second intervals

Make Ahead
All three components, mushroom filling, leek filling, and custard, can be made up to 2 days ahead and refrigerated separately. The potato shells can also be pre-baked ahead and stored at room temperature. Assemble and bake just before serving for the freshest result.