Don't stop with eggs, butter, salt and pepper. Here are some possibilities suitable for adding variety to both scrambled eggs and omelets. Keep in mind that additions should be chopped fairly small, and that they should not be soupy:
* Persillade, a combination of garlic and parsley. A good mix is three or four tablespoons of parsley leaves chopped with one medium-sized clove of garlic. This amount should be enough for six people.
* Cheese. Add grated cheese -- cheddar, jack, swiss-type or goat cheeses are great -- at the rate of about one tablespoon per person.
* Peppers, onions and tomatoes. To add to eggs for six to eight people: in two tablespoons of butter or good olive oil, saute' one finely chopped small onion, half a large green pepper and half a large red bell pepper, both finely chopped, and one teaspoon of very finely minced garlic until the vegetables are softened. You can add a small jalapeno or other hot pepper at the same time, if you like spicy foods. Drain two 14 1/2-ounce cans of stewed or plum tomatoes, and chop the tomato flesh roughly and add them to pan, or an equal amount (three or four tomatoes) of peeled, seeded and chopped fresh tomatoes. Add the tomatoes to the onion mixture and let simmer over medium-low heat until the liquid in the vegetables has nearly cooked away. You can add spices, too, if you wish, toward the end of cooking. Some ideas: ground cumin, dried crumbled oregano, fresh finely chopped coriander or parsley. If you are using canned tomatoes you probably won't need salt.
* Spinach, chopped fine and saute'ed together with some shallot or scallion, also finely chopped, and salt and pepper, in a little butter just long enough to get most of the moisture out. You can add a little whipping cream to the spinach too, but not enough to make it soupy. Spinach can be mixed in to eggs for omelets before they are cooked, or used as a filling.
* Chicken livers, sauteed with a little minced onion, shallot or scallion and salt and pepper, then chopped.
* Mushrooms, wild, regular, or a combination of wild and regular. A pound of mushrooms will be enough for eggs for six to eight. Saute' a pound of cleaned, sliced mushrooms in three tablespoons of butter until the mushrooms have exuded their juices and begun to dry out. Add salt and pepper, and if desired, a few tablespoons or so of the persillade (parsley and garlic) mentioned above. You can also add 1/4 cup or so of whipping cream at the end, letting it simmer a minute to reduce and thicken slightly.
* Truffles. Truffles are terrific with eggs. Add them sliced or grated when the eggs -- either scrambled or in omelet form -- are very nearly done, just to heat them through.
* Caviar, with or without sour cream. It's best, so as not to disperse the elegant flavor of the caviar, to serve it on top of scrambled eggs (not mixed in) or folded inside the omelet. Garnish the omelet with a dab of sour cream and a few stray bits of caviar.
* Fresh herbs. Although the time for outdoor herbs has passed for this season, if you are lucky enough to find a source for them in midwinter by all means take advantage. While we're admonished with all kinds of do's and don'ts about which herbs go together and which don't, it is actually next to impossible to find a combination of fresh herbs that doesn't work with eggs. Herbs for both omelets and scrambled eggs should be mixed in with the raw eggs before they are cooked. Use about a tablespoon, chopped fine, per serving.
* "Fried-out," drained, crumbled bacon, duck or goose cracklings, saute'ed sausage pieces, or slivers of ham.
* Combinations: cheese together with anything on the list except caviar or truffles; persillade with anything on the list except caviar or truffles; the tomato mixture with ham or sausage, spinach with mushrooms are some of the more obvious.