Remove the rind from the brie. Slice into thin small slices, keep running the knife under water so the cheese won't stick. Set aside.
Slice mushrooms, sauté until mushrooms are golden, lightly season with salt and pepper.
Add the brie slices to baguette (if any slices are thick, with wet hands, flatten them). Add mozzarella cheese. Add the sautéed mushrooms (ham, asparagus, ham and spinach if desired). Bake another 3-4 minutes.