For the mushroom bread au gratin, clean the mushrooms, wash them and cut them into equal pieces. Heat the pan, add the mushrooms, stirring frequently to evaporate the liquid from the mushrooms.
Add onions, garlic and olive oil and roast, season with salt, pepper and thyme and let cool.
Stir in cream cheese and yolks, season again. Divide mushroom mixture among 4 loaves, place on baking sheet lined with parchment paper and bake on middle rack until golden brown, 8-10 minutes.