Begin by preparing shrimp and boneless chicken breast. Cook shrimp in boiling water for about 5 minutes, depending on size, until pink and firm. Poach chicken breasts according to the recipe Boneless Chicken Breasts for Salads.
Review baking instructions for puff pastry shells, preheat oven, and bake shells. Toast can be used as an alternative; cut into triangles.
In a 3 quart sauce pan, over medium heat, melt 3 tablespoons of butter or margarine. Add flour, salt, pepper, and cayenne and whisk until smooth.
Gradually whisk the preheated milk and chicken broth into the flour mixture and bring to a slow boil, stir frequently. Continue cooking until mixture is thick and smooth. Stir in sherry, chicken, shrimp and crab.
While preparing the sauce, use a medium skillet to melt the remaining 3 tablespoons butter or margarine over medium-high heat. Saute the onion, mushrooms, parsley and chives until tender. Reduce any liquid.
Combine the seafood and mushroom mixtures. Serve over toast points or puff pastry.