Step 1: Preheat the Oven. Preheat your oven to 375°F (190°C). Allow at least 10-15 minutes to reach the desired temperature.

Step 2: Prepare the Seafood. Rinse and pat dry the shrimp, scallops, and white fish using paper towels. Cut the fish into bite-sized pieces.

Step 3: Sauté the Garlic. Melt butter in a skillet over medium heat, add minced garlic and sauté for about 1 minute.

Step 4: Cook the Seafood. Add shrimp, scallops, and white fish to the skillet with garlic. Cook for 3-5 minutes until seafood is opaque.

Step 5: Prepare the Creamy Sauce. Whisk together heavy cream with salt and black pepper in a mixing bowl. Pour over sautéed seafood in the skillet.

Step 6: Add Fresh Herbs and Cheese. Stir in chopped parsley and half of the Parmesan cheese, mixing well.

Step 7: Transfer to Baking Dish. Grease a baking dish and transfer the seafood mixture, spreading evenly. Top with remaining cheese.

Step 8: Add the Crunchy Topping. Sprinkle Panko breadcrumbs on top, covering the surface properly.

Step 9: Bake to Perfection. Bake in preheated oven for 25-30 minutes until bubbling and golden-brown.

Step 10: Let it Rest. Allow the gratin to cool for about 5 minutes before serving.