To prepare an au gratin cheese recipe, first you need to prepare the asparagus. First, you'll need the following ingredients: 2 tablespoons butter, 2 teaspoons kosher salt, 1 tablespoon melted swiss cheese, and 1 teaspoon thyme. In a large bowl, toss the ingredients together until the cheese is evenly distributed. Pour the mixture into the bottom of an 8-inch-square baking dish. Sprinkle the top of the dish with shredded Parmesan cheese. Bake in the preheated oven for 20 minutes. Remove from the oven and allow to cool for 5 minutes before serving.