OMELET FILLINGS Almost any food can fill an omelet. To invent your own filling, use 1 or more filling ingredients to total about 1/3 to 1/2 cup for each omelet. Flavor the omelet, filling or both with about 1/8 to 1/4 teaspoon of your favorite herb or spice or a seasoning blend from a salad dressing, soup or other flavoring mix. Fill an omelet right after you've finished cooking it. At this point, the omelet will be hot enough to melt cheese and warm some filling ingredients such as yogurt, peanut butter, or diced or sliced fruit. Heat refrigerator-cold fillings to serving temperature or fully cook raw foods before you begin cooking the omelet.