From America's Test Kitchen Season 2: Bacon, Eggs, and Homefries
A cheese omelet should have a light, tender texture and a creamy interior filled with completely melted cheese. We wanted a foolproof method that would keep all of that delicious filling inside a soft, lightly colored egg casing.
First, a few basics. A good-quality, nonstick skillet with gently sloped sides is the best pan for a great omelet. Beating the eggs thoroughly ensures uniform texture inside and outside of the omelet. In addition, we stirred the eggs after adding them to the skillet; eggs cooked without stirring produced an uneven, loose omelet. We determined that half-and-half, cream, milk, and water all diffused the egg flavor and should not be added. Butter, however, added rich flavor.
We then set out to refine our technique using three-egg cheddar omelets as our master recipe. Simply folding the eggs around the cheese was insufficient to contain it, but the traditional French method of tilting and jerking the pan to shape the omelet worked perfectly. Removing the pan from heat after the eggs set up ensures that they never become too brown, rubbery, or tough. The one drawback was that our cheese no longer melted completely, so we made the simple change of using more finely grated cheese. Harder cheeses still failed to melt completely, but many other cheeses work well. The only rule of thumb for these light, delicate omelets is to use softer cheeses that can be grated.
Making perfect omelets takes some practice, so don’t be disappointed if your first effort fails to meet your expectations.