Grease a small baking dish with a little butter and first fill it with the ham cut into small cubes. Now add the egg and cream, as well as the spinach leaves and the sliced mushrooms. Sprinkle the grated cheese on top and season everything vigorously with salt and pepper.
Put the casserole in the oven for about 15-20 minutes and enjoy while still warm.
The recipe can be varied as you like, for example by adding salmon instead of the cooked ham or using other vegetables such as peppers or tomatoes.