Melt butter in wok or skillet; stir-fry mushrooms and onions over very low heat. (Butter will burn if heated over 225 Â°F.)
Remove; set aside.
Beat eggs with salt and pepper.
Pour into wok; heat slowly.
Lift up edges of eggs as they become set on bottom; let uncooked egg run under.
Cook until golden brown on bottom and creamy on top.
Place mushrooms and onions in center; roll onto plate.
Garnish with lettuce or parsley