Preheat oven to 325 degrees F.

Melt the butter in a skillet over medium heat.

Add the diced bell pepper, onion, and celery to the skillet.

Sauté the vegetables for 2 minutes, until softened.

In a bowl, combine the cream of shrimp soup, mayonnaise, and Parmesan cheese.

Add the crabmeat, shrimp, and white pepper to the bowl.

Stir the sautéed vegetables into the seafood mixture.

Spoon the mixture into a lightly greased 8 x 11-inch casserole dish.

Bake in the preheated oven for 30 minutes, or until bubbly and golden brown.

Serve hot with toast points or crackers.