Wash the parsley, dab dry and remove the leaves. Put 3 leaves aside, cut the rest into fine strips. Separate the eggs. Beat egg whites until stiff. Stir in lemon juice and egg yolks. Sieve the starch over the egg yolks, fold in and season with salt, pepper and nutmeg.
Grease a coated pan (approx. 22 cm Ø) with 1 tsp. margarine. Place whole parsley leaves in it and heat up. Pour egg foam mixture on top. Cover and let it simmer at low heat for about 20 minutes. Halve the mushrooms. Wash, quarter and seed the tomatoes. Cut the flesh into strips. Heat 1 teaspoon margarine in a pan. Fry the mushrooms for about 5 minutes. Season with salt and pepper. Add tomato strips.
Cut the flesh into strips. Heat 1 teaspoon margarine in a pan. Fry the mushrooms for about 5 minutes. Season with salt and pepper. Add tomato strips. Deglaze with 100 ml water, stir in broth, bring to the boil briefly once. Cover half of the omelette with the mushroom mixture, fold the other half over. Sprinkle with parsley strips and garnish with parsley