Mashed Potato Crust Quiche Recipe with Crisp Edges

Mashed potato crust quiche is a savory baked egg pie with a tender potato base instead of pastry, filled here with spinach, onion, cheddar, and a simple cream custard. The potato crust is easy to press into a pie plate, and baking it before adding the filling helps it hold together and develop crisp edges.

Ingredients

1 teaspoon (5 ml) neutral oil or softened butter, for greasing the pie plate
2 1/2 cups (560 g) cold, plain mashed potatoes, preferably firm rather than loose
1 large egg (50 g without shell), for binding the potato crust
1/4 cup (25 g) finely grated Parmesan cheese
2 tablespoons (16 g) all-purpose flour
1/2 teaspoon (3 g) fine salt, divided, plus more to taste
1/4 teaspoon (0.5 g) ground black pepper, divided
1 tablespoon (14 g) butter
1 cup (150 g) finely chopped yellow onion, about 1 small onion
1 cup (30 g) chopped fresh spinach, loosely packed
1 cup (110 g) shredded sharp cheddar cheese
4 large eggs (200 g without shells), for the filling
1 cup (240 ml) whole milk
1/2 cup (120 ml) heavy cream
1/8 teaspoon (0.25 g) ground nutmeg, optional

Instructions

Set a rack in the middle of the oven and heat it to 425°F (220°C). Lightly grease a 9-inch (23 cm) pie plate with the oil or softened butter, paying attention to the bottom and the curve where the sides meet the base. Use a standard metal or ceramic pie plate; a shallow tart pan can hold less filling, so do not force all the custard into it.
In a medium bowl, combine the cold mashed potatoes, the crust egg, Parmesan, flour, 1/4 teaspoon of the salt, and half of the black pepper. Stir until evenly mixed. The mixture should be thick enough to hold a shape when pressed. If your potatoes are unusually soft or wet, mix in another tablespoon of flour; if they are stiff and crumbly, work in a teaspoon of milk at a time. Avoid adding liquid unless needed, because a loose crust is harder to crisp.
Transfer the potato mixture to the prepared pie plate. With damp fingertips or the back of a spoon, press it evenly over the bottom and up the sides, aiming for a layer about 1/4 inch (6 mm) thick. Smooth the bottom so there are no deep pockets, and make the upper edge a little thicker than the base to help it stay intact. Bake the crust for 22 minutes, until its surface looks dry and the edges are beginning to turn golden. It will not be as crisp as pastry at this stage.
While the crust bakes, melt the butter in a skillet over medium heat. Add the onion and cook for about 5 minutes, stirring now and then, until softened and translucent but not deeply browned. Add the chopped spinach and cook for 1 to 2 minutes, just until wilted. If liquid collects in the skillet, continue cooking briefly until most of it evaporates. Set the vegetables aside while you prepare the custard.
When the crust is ready, take it out of the oven and reduce the oven temperature to 350°F (175°C). Sprinkle the shredded cheddar over the crust, then spread the onion and spinach evenly on top. Distributing the cheese and vegetables before pouring the custard helps prevent the filling from settling in one spot.
In a bowl, whisk the 4 filling eggs with the milk, cream, remaining 1/4 teaspoon salt, remaining black pepper, and nutmeg if using. Whisk until the yolks and whites are fully blended, but do not beat so much that the mixture becomes foamy. Pour the custard slowly over the filling. If the pie plate is very full, place it on a rimmed baking sheet before returning it to the oven.
Bake at 350°F (175°C) for about 38 minutes, until the outer portion is set and the middle has only a slight movement when the plate is gently nudged. The USDA FSIS safe minimum for egg dishes is 160°F (71°C); check the center with a food thermometer, making sure the tip reaches the custard without touching the pie plate. If the center is below that temperature, continue baking and check again after a few minutes. If the potato edge is browning too quickly, loosely cover just the edge with foil.
Set the quiche on a heat-safe surface and let it rest for 10 minutes before slicing. This short rest allows the custard to finish settling, so slices are easier to lift and less likely to slump. Cut into 6 wedges with a thin knife, wiping the blade between cuts if you want neater portions.

Tips

Start with cool, fairly firm potatoes. Leftover mashed potatoes work well, as do freshly made potatoes that have cooled enough to handle. Very loose potatoes can make the crust soft; avoid adding extra milk or butter to the crust mixture, and use the small flour adjustment only if it is still too wet to press.
Press an even layer and prebake it fully. Thin patches can split when you serve the quiche, while very thick areas may stay soft. Make sure the bottom is level and the sides are supported. The crust should look dry before you add the filling; skipping or shortening the prebake can leave a damp layer beneath the custard.
Keep the vegetables from watering down the custard. Cook the onion and spinach until excess moisture has evaporated. Frozen spinach is also suitable: thaw it completely, squeeze it very dry, then measure about 1/2 cup (75 g) squeezed spinach in place of the fresh spinach. Wet vegetables can make the center loose even when the eggs are cooked.
Season the potatoes according to how they were made. If your mashed potatoes already contain salt or Parmesan is especially salty, use less added salt and taste the cooked onion mixture before assembling. For a gluten-free crust, replace the all-purpose flour with the same amount of a finely milled gluten-free flour blend; the crust may be a little more delicate but should still press into the plate.

Serving Suggestions

Serve the quiche warm, at room temperature, or just slightly cooled. For brunch, pair a wedge with a crisp green salad dressed with lemon vinaigrette, sliced tomatoes, or fresh fruit. At lunch, add a bowl of vegetable soup or roasted vegetables for a more substantial plate. The rich custard and potato crust benefit from something bright or lightly dressed alongside them, rather than another heavy side.

For a casual gathering, bake the quiche shortly before guests arrive and let it rest while you set out salads and other sides. It slices more cleanly after its 10-minute rest, but it does not need to be piping hot to taste good. If serving it at room temperature, keep the total time out of refrigeration within the food-safety limit described below.

Variations

Change the cheese: Replace the cheddar with Gruyère, Swiss, or Monterey Jack in the same quantity. Gruyère brings a nuttier, more pronounced flavor, while Monterey Jack is milder and melts smoothly. A small amount of crumbled feta can also be used, but reduce the added salt because feta is often salty.

Add cooked meat: Stir up to 3/4 cup (100 g) cooked, crumbled bacon, diced ham, or cooked breakfast sausage into the filling with the vegetables. Cook meat separately before adding it; the time in the quiche is intended to set the custard, not cook raw meat safely. For a vegetarian version, replace the spinach with chopped cooked broccoli or sautéed mushrooms, draining excess liquid first.

Use another vegetable: Try 1 cup (100 g) chopped roasted red pepper, cooked mushrooms, or steamed broccoli florets. Cut vegetables into small pieces so each slice holds together. Cook or drain them before assembly, since raw watery vegetables can release liquid into the custard as it bakes.

Make the flavor sharper: Add 1 teaspoon (5 ml) Dijon mustard to the egg mixture, or replace up to half the cheddar with a stronger aged cheese. A pinch of smoked paprika or a little chopped chive is another easy addition. Keep the total filling quantity close to the recipe so the custard can set within the stated baking time.

Storage and Reheating

Do not leave the cooked quiche at room temperature for more than 2 hours. Once it has cooled enough to handle, cover the pie plate or transfer slices to a sealed container and refrigerate. It keeps for 3 to 4 days in the refrigerator. For easier reheating, store individual slices with parchment between them so they can be removed without breaking the potato crust.

To reheat a slice, place it on a baking sheet in a 325°F (165°C) oven for about 15 to 20 minutes, depending on its thickness, until hot throughout. Reheat leftovers to 165°F (74°C), checking the center with a food thermometer. A microwave is quicker: heat a slice in short intervals, checking that it is hot all the way through, though the crust will be softer. To freeze, wrap fully cooled individual slices tightly and freeze for up to 2 months for best quality. Thaw overnight in the refrigerator before reheating; freezing can make the custard slightly less silky.

Frequently Asked Questions

Can I make mashed potato crust quiche ahead?
You can bake the crust up to a day ahead. Cool it, cover it, and refrigerate it; add the prepared filling and bake when ready, allowing a few extra minutes if the crust and filling are cold. You can also bake the complete quiche a day ahead, refrigerate it within 2 hours, and reheat it in the oven before serving.

Can I use instant mashed potatoes?
Yes, provided they are made thick and allowed to cool before mixing. Prepare them according to the package directions, but avoid adding more liquid or butter than needed for a firm mash. Instant potatoes can vary in absorbency, so if the crust mixture feels loose, add flour a tablespoon at a time until it can be pressed into an even layer.

Why did my potato crust fall apart?
A crust may crumble if the potatoes were dry and coarse, the mixture lacked a binder, or the base was pressed too thin. The egg and flour help bind it, while the short rest after baking helps slices hold. Use a thin, flexible spatula to lift wedges and avoid cutting while the quiche is piping hot.

How can I tell when the quiche is done?
The outer filling should look set and the center should no longer appear liquid. A slight wobble is normal, but use a food thermometer to confirm that the center reaches 160°F (71°C), the USDA FSIS safe minimum for egg dishes. Oven temperatures and pie plates vary, so the thermometer is more dependable than timing alone.

Can I make it without cream?
Yes. Replace the 1/2 cup (120 ml) heavy cream with an equal amount of whole milk. The result will be somewhat less rich, but the egg-to-liquid ratio should still set properly. Avoid replacing the cream with a very thin, watery liquid, and keep the total milk and cream amount at 1 1/2 cups (360 ml).

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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes

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