Fluffy frittata with spinach

⏲ ~27 min total · prep 11 · cook 16 · 4 servings

By the KFI Test Kitchen · Tested & approved by Jason Lieu, KFI recipe editor

Published Sep 15, 2026 · Updated Sep 15, 2026

Ingredients

• 8 large eggs, separated
• 1/4 cup heavy cream
• 1 cup low-moisture mozzarella, shredded
• 5 oz baby spinach
• 3 tbsp butter, divided
• 1 small shallot, minced
• 1/4 tsp ground nutmeg
• Salt and black pepper

Instructions

1. Heat the oven to 375°F with a rack in the upper third.
2. Melt 1 tbsp butter in a 10-inch oven-safe nonstick skillet over medium heat, add the spinach in handfuls, and wilt it for 2-3 minutes, adding the shallot for the last minute. Turn the spinach into a colander and press out the moisture with a spatula — wet spinach will collapse the soufflé effect.
3. Whisk the yolks with the cream, 1/2 tsp salt, pepper, and nutmeg until smooth.
4. Beat the whites with a clean whisk until they hold soft, droopy peaks.
5. Fold the yolk mixture into the whites in two additions, keeping the batter as airy as possible, then fold in the spinach and mozzarella.
6. Melt the remaining 2 tbsp butter in the same skillet over medium-low, pour in the batter, and smooth the top. Cook 3 minutes, until the edges bubble.
7. Bake 12-14 minutes, until the frittata is puffed about 2 inches, golden on top, and a knife in the center comes out clean.
8. Serve immediately from the skillet — like a soufflé, it sinks as it cools.

Why this recipe works

• Whipped whites Beating the whites separately and folding them back in is what lifts this frittata close to two inches in the oven. Ordinary frittatas stay flat.
• Squeezed-dry spinach The wilted spinach gets pressed in a colander, so the water that would collapse the batter never reaches the pan.
• Nutmeg with spinach A quarter teaspoon of ground nutmeg is the classic partner for cooked spinach, and here it seasons the whole batter instead of one spot.

Tips for making this recipe well

Soft peaks only

Stop beating when the whites hold soft, droopy peaks. Stiff whites fold poorly and leave the batter chunky instead of airy.

Fold in two additions

Add the yolk mixture to the whites in two goes and fold gently each time. Dumping it in at once knocks the air out, and the air is the entire lift.

Press the spinach hard

Push the wilted spinach against the colander with a spatula until nothing more runs out. Wet spinach is the main reason soufflé-style frittatas fall.

Serve it standing

Carry the skillet to the table the minute it leaves the oven. Like a soufflé, it sinks as it cools, and the tall moment is worth catching.

Serving suggestions

Bring the skillet straight to the table and cut wedges in front of everyone, because the two-inch puff settles as it cools and the first view is the tall one. The nutmeg and mozzarella carry it without sauce or garnish. At 4 net carbs per serving it fits a keto day without much planning, and a green salad alongside turns 40 minutes of work into a proper supper.

Storage and meal prep

This frittata is at its height in the first half hour, while any puff remains. Leftover wedges keep 3 to 4 days covered in the refrigerator and reheat gently in a low oven or a covered skillet; they will be flat but still tender thanks to the whipped whites. Freezing is a poor match, since thawed egg white turns weepy and the airy set is the whole point of the dish.

Variations worth trying

• Change the cheese Gruyère or crumbled feta replaces the mozzarella in the same amount.
• Add soft herbs A tablespoon of chopped dill or chives folded in with the spinach leans the flavor fresher.
• Mushroom version Brown a handful of sliced cremini with the shallot and let them steam dry before folding in.

Frequently asked questions

Why separate the eggs?

Whipped whites trap air, and that air expands in the oven to lift the frittata close to two inches. Beaten whole eggs cannot produce the same rise, which is why standard frittatas bake flat.

Can I make it ahead?

It is built to be eaten immediately, since it sinks as it cools. You can wilt the spinach and whisk the yolks earlier in the day, then beat the whites and bake right before serving.

Do I have to use nutmeg?

It is traditional with spinach and easy to skip. A quarter teaspoon never reads as spice; it rounds out the eggs.

Why did mine fall flat?

Wet spinach or heavy-handed folding, in that order of likelihood. Both drive the air out, and the air is the lift. Press the spinach until it stops dripping and fold in two additions.

Can I use frozen spinach?

Thaw it completely and squeeze it dry before it touches the batter. Frozen spinach holds even more water than fresh, so press harder than feels reasonable.

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