Bring water & 1 ts salt to boil in pan, add mushrooms, & cook over moderate heat for 2 mins.
Drain well, cool, & cut mushrooms into thin slices.Heat 1 tb butter or margarine in skillet, add mushrooms, & stir-fry over moderate heat for 2 mins.
In separate skillet, heat 1 tb butter or margarine, add onions, & stir-fry over moderate heat until golden, abt 3 mins. Add them to mushrooms.
Beat eggs well, stir in parsley w/remaining 1/2 ts salt, & pour eggs over mushrooms & onions.
Cover skillet & fry over low heat for 3 mins to set eggs & lightly brown bottom of omelet.
Do not turn over. Serve warm. Serves 4 as appetizer.