Chop the onion, heat 25 g butter, fry the onion cubes until translucent, sprinkle with the oyster mushrooms, season with salt and pepper. After a few minutes, add a dash of white wine and a splash of lemon juice and cook for 5 minutes.
Butter a casserole dish, beat 1 egg white until stiff, mix the egg yolks with the cream and parsley and fold into the mixture. Fold in the egg whites, bake at 200 ° C for 8 min