1/4 teaspoon Kosher salt
1/4 cup grated Gruyere cheese
1) Preheat the oven to 230 degrees Celsius with a rack in the middle. Line a baking sheet that can take high temperatures without warping, with parchment paper
2) Separate the egg yolks from the whites. Make sure there aren’t any pieces of egg yolk in the whites or you will have difficulty getting the whites to beat properly. It helps if you are making more than one egg nest to keep each egg yolk in a separate prep bowl.
3) Place the egg whites in a very clean mixer bowl (any residual oil in the mixer bowl will keep the egg whites from whipping up properly). Add a quarter teaspoon of salt to the egg whites. Beat the egg whites with a whisk attachment in a mixer (or using a hand mixer), starting on low speed and then slowly increasing to high speed, until stiff peaks form.
4) Gently fold in the grated Gruyere cheese, taking care not to deflate the egg whites.
5) Create two mounds of the egg white mixture on the lined baking sheet. Form the mounds so they look like nests, with indentations in the centers.
6) Place in the oven for 3 minutes. After 3 minutes, open the oven, pull out the rack with the egg white nests, and gently add an egg yolk to the center of each nest. Return the baking sheet to the oven and cook for 3 more minutes.