Preheat oven to 350°F; butter 8-inch square baking dish and set aside.
In a sauté pan, melt butter until it foams and add flour slowly to form a paste. Slowly add milk and stir until sauce coats spoon, about 5-7 minutes Add salt. Remove from heat and set aside.
Marinate shrimp, scallops in wine for 10 minutes In a sauce pan, sauté onion until soft, then add mushrooms.
Add shrimp, scallops and wine and stir to coat with onions. Add garlic, salt and pepper and cook until shrimp and scallops are cooked, about 5 minutes
Remove pan from heat and drain liquid into a 2 cup glass measuring cup. Set aside. Add enough white sauce to the shrimp liquid to make 2 cups.
Put rice in prepared baking dish. Top with shrimp mix. Pour white sauce on top until shrimp and rice are covered. Sprinkle cheese on top. Bake 10-12 minutes until bubbly and cheese melts. Garnish with parsley and serve hot.