Stew the onion and garlic cubes in a pan. Add the mushroom slices and cook until the water has evaporated. Remove from heat, season with salt and pepper, pour in the cream, mix and let cool down a little.
Roll out the puff pastry thinly and place on the tray. Spread the cheese on top. Beat the eggs, mix with the mushroom mixture and distribute everything on the dough. Bake at 240 ° C on the lowest rack of the preheated oven for about 25-30 minutes.
Sufficient for 2 people, for 4 people or a baking sheet of approx. 30 x 33 cm. Use twice the amount.