Crab Gratin

Preheat oven to 425 degrees. Set shelf about 5-6 inches under the broiler. Lightly butter the casserole or shells. Melt 4 tablespoons of butter in a heavy 2 or 2 1/2 quart saucepan. Use medium heat. When melted, add flour, stirring with a wooden spoon. Cook 2-3 minutes after mixture is frothy. Add milk and cream all at once. They should be at room temperature or warmer. Stir until sauce is thickened and smooth. Add vermouth and lemon juice. Cook for several minutes. Taste and adjust seasonings as needed with salt and pepper. To hot sauce, slowly add about 2/3 of the grated cheese. Stir until smooth. Do not boil. This can be done ahead and held, off heat, until ready to finish. To hot mixture, add crab meat. Fold in carefully to avoid breaking up the lumps of meat. When mixed and warmed through, put mixture in casserole or shells. Do not fill to the edge. Sprinkle remaining cheese on the surface. Dot with remaining butter and dust lightly with paprika. Put casserole or shells in oven, and bake for about 4 minutes. As soon as mixture starts to bubble, put under the broiler for a minute or two, just enough to color the surface. Serve immediately. Ingredients for 4 servings as a main course or 6 as a first course.