In a preheated pan heat the olive oil and sautée the leek and garlic cloves with salt.
Add the quartered mushrooms and the butter. Cook until the mushrooms are soft.
Add the fresh thyme and spinach and let simmer. After the spinach is cooked add the croutons and stir well.
Add the crumbled goat cheese and remove from the heat.
Spread the dough, spread the filling on top and shape the dough. Cover with egg yolk and decorate with pieces of the butter dough. Bake at 200 degrees for 30 minutes.
Decorate with fresh rosemary and serve with yogurt sauce.