Beat together eggs, water, salt, and pepper.
Melt butter in an omelette pan or skillet until very hot but not brown or smoking.
Pour in egg mixture and cook over a medium heat, lifting the edges with a spatula to allow the liquid to run underneath.
When omelette is golden brown on the bottom but still creamy on top, fold one half over the other and slide onto a warm platter.
May be served with Mushrooms in Cream or Creole Sauce.
Spoon sauce around the omelette and garnish with watercress.