But even the practical frittata requires a little know-how, lest the bottom turn rubbery or the center end up loose and wet. I wanted to uncover the keys to a tender, evenly cooked, cohesive frittata. I also wanted it to be big and hearty enough to serve at least four for dinner.

Stir and Scrape

With plenty of filling ingredients and a 12-inch nonstick skillet at the ready, I evaluated common cooking methods.  I immediately dismissed what I call “the inversion method,” since it can be even harder to pull off than folding an omelet. It calls for cooking the frittata in an oiled skillet on the stove until the bottom sets, sliding it onto a plate, placing the overturned skillet on top of the frittata, inverting it back into the skillet, and returning the skillet to the stove to finish cooking. Yes, it’s as tricky as it sounds. No thanks.

Instead, I tried a method that skips the difficult flipping step and calls for covering the skillet to trap the steam and cook the eggs through. I poured a dozen beaten eggs (enough to serve four to six people) on top of 3 cups of a hot placeholder filling (the right amount for a substantial frittata) and gave it a try. Unfortunately, this was a miss: While I waited for the eggs to set, the bottom of the frittata overcooked.

Another popular approach, cooking the frittata entirely in the oven, didn’t fare much better. Recipes were either too time-consuming, requiring a low temperature and at least 40 minutes to cook the eggs, or they called for the use of a broiler, which produced a spotty brown top that hid runny pockets.

In the end, I got the best results using a hybrid stove-oven approach. But it wasn’t as straightforward as pouring the eggs over a filling on the stovetop, letting it cook for a couple of minutes, and then popping the pan into the oven. When made this way, the frittata overcooked on the bottom.

Stirring the eggs as they began to set on the stovetop was crucial. After pouring the eggs over the filling, I scraped the bottom of the pan as curds formed. This action prevented overcooking by pushing the partially cooked egg away from the pan bottom and allowing raw egg to flow in. After just 30 seconds, my spatula left a wide trail through the curds, at which point I smoothed the eggs into an even layer and transferred the skillet to a 350-degree oven, where the frittata finished cooking in less than 10 minutes. Progress, indeed: This frittata was evenly cooked from top to bottom and edge to edge. However, the eggs were rather rubbery. Here was my next challenge.

The Trail to Success

Stirring the eggs with a rubber spatula as they cook on the stovetop helps all the eggs set up evenly. When the spatula leaves a trail in the skillet, it’s time to transfer the pan to the oven. Look for a trail that fills in slowly; if it fills in quickly, not enough egg has coagulated, and the finished frittata will contain pockets of undercooked egg.

The Proteins That Bind

Many frittata recipes call for the addition of dairy, claiming that it tenderizes eggs. So I whipped up frittatas using milk, heavy cream, sour cream, and crème fraîche, happily finding that they all produced roughly the same tender texture—any variation in richness wasn’t noticeable because of the substantial filling. And because any subtle flavor differences in the dairy were also obscured by the filling, I settled on milk. One-third cup of milk per dozen eggs was just the right amount. Any more made the eggs too delicate.

It was at this point that a colleague made an interesting observation. The frittata was emerging piping hot from the oven; when I took its temperature, it registered between 185 and 195 degrees. Scrambled eggs cooked to that temperature would be tough and bouncy—and yet the frittata was still tender. Exactly what was the milk doing to keep the eggs tender?

Here’s what I learned: First, when it comes to tenderizing eggs, there’s nothing special about dairy; any liquid will do the job. That said, after experimenting with water (too bland), chicken broth (too chicken-y), and even wine (too acidic), I decided to stick with understated milk.

That’s where the extra liquid comes in: Liquid dilutes the proteins, making it harder for them to coagulate and turn rubbery even as the temperature rises. What’s more, even when they do bond, there is a lot of extra water in the mesh, which further contributes to tenderness. The result is eggs that remain tender even when heated to nearly 200 degrees. As I read about egg cookery, I was reminded that the salt I was using for seasoning also played a role in protein coagulation. Salt weakens the protein network, a disruption that further tenderizes the eggs.

Two Great Egg Tenderizers: Liquid and Salt

The combination of milk and salt gives our frittata its tender texture. The addition of any type of liquid makes it more difficult for egg proteins to bond, and when they do bond, they hold more moisture that contributes to increased tenderness. Salt weakens the protein networks, further tenderizing the eggs. The upshot is softer, more tender curds, even at relatively high temperatures. To demonstrate this concept, we cooked batches of eggs sous vide in plastic containers and then placed weights on top to gauge their tenderness.

Filled to Capacity

To finish, I drew up some guidelines for the fillings. First, I chose bold ingredients to complement the mild eggs, cooking them in the skillet before building the frittata. Second, I chopped the ingredients into ½-inch pieces (or smaller) because large chunks broke up the frittata’s structure, making it prone to falling apart. Third, I seasoned not just with salt but also with a touch of acid, which provided a flavor boost without affecting the texture of the eggs.

Fill 'er up with Small Pieces

Taking the time to cut the filling ingredients into small pieces improves the frittata’s cohesiveness. The eggs can easily surround small pieces of filling and hold them in place, whereas larger pieces can lead to gaps in the frittata, making it prone to breaking.

My first creation was a broccoli and feta frittata seasoned with lemon and red pepper flakes. As I worked my way through other combinations, three favorites emerged: asparagus with tangy goat cheese, Yukon Gold potatoes paired with garlicky chorizo, and earthy shiitake mushrooms with nutty Pecorino Romano cheese. Move over, omelets—when eggs are for dinner, a simple frittata will be my new go-to dish.

Keys to Success

• Tender eggs

  Additions of milk and salt allow the eggs to cook to a relatively high temperature without becoming rubbery.

• Punched-up flavor

  Seasoning a bold filling with not just salt but also an acidic ingredient (such as citrus juice or vinegar) enhances its flavor.

• Evenly cooked texture

  Stirring the eggs while they cook on the stove helps them cook evenly; finishing the frittata in the oven lets it finish cooking gently.

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