Knead 300 g flour, fat in flakes, 1/2 tsp salt and 1 egg to a smooth dough. Cover and chill for about 1 hour.
Clean the mushrooms, wash if necessary and cut in half depending on the size. Peel and finely chop the onion. Sauté the mushrooms in hot oil. Add onion and fry briefly. Season with salt and pepper. Let cool off
Wash and chop the parsley. Mix 4 eggs, milk and parsley. Season with salt, pepper and nutmeg
Grease a tart mould with removable base (approx. 28 cm Ø) or a springform pan. Roll out the dough on a little flour until round (approx. 34 cm Ø). Put it into the tin and press up the edge by about 3 cm. Prick the base more often. Spread mushrooms, salmon and egg milk on top. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/gas: level 2) for 50-60 minutes