To prepare a three cheese broccoli manicotti recipe, first you need to prepare the ingredients. First, you'll need the following ingredients: 2 tablespoons butter, 2 teaspoons kosher salt, 1/2 teaspoon thyme sprigs, 1 tablespoon olive oil, and 1 teaspoon garlic powder. You will also need 2 cups shredded mozzarella cheese, 1/4 cup ricotta cheese and 1/2 cup Parmesan cheese. Place the cheese mixture in the bottom of an oven-proof dish and bake for 20 minutes. Remove the dish from the oven and let it cool for 5 minutes before serving.