Preheat oven to 350 degrees.
Melt butter in a large pot.
Add ground walnuts to the butter and whisk until smooth.
Add onions, mayonnaise, salt, and stock. Once again mix until smooths out then let it cook until thh mixture thickens.
Using a spoon or ladle put a layer of sauce at the bottom of a greased pan. Then put a layer of the sliced cauliflower. Repeat this until it is layerd and full almost to the top.
Put a thick layer of mozzarella cheese on top. Then sprinkle the garlic powder and black pepper to taste.
Bake until golden brown which should be about 90 minutes.