Brush the chops with mustard, season with salt and pepper. Cut the onions into slices and cover the greased baking sheet with the chops. Cover with aluminum foil and pierce a few small holes.
Cook in the oven for 1 hour at 200 degrees.
Season the whipped cream with salt and pepper. Then remove the foil, cover the meat with mushrooms, pour the seasoned cream over everything.
Put in the oven for another 30 minutes without foil.