Ingredients

• 1 1/2 pounds unpeeled, large fresh shrimp
• 1 1/2 pounds sea scallops
• 2 1/2 cups half-and-half
• 2 (8-ounce) packages fresh mushrooms, sliced
• 1 cup butter or margarine, divided
• 2/3 cup grated Parmesan cheese
• 2/3 cup shredded Swiss cheese
• 1/3 cup all-purpose flour
• 1/4 cup minced shallots
• 3 tablespoons dry sherry
• 1 tablespoon lemon juice
• 1 teaspoon Dijon mustard
• Pinch of ground nutmeg
• 1/2 teaspoon salt
• 1/4 teaspoon ground white pepper