Chicken cordon blue casserole

¼ cup butter or margarine
¼ cup flour
¼ teaspoon salt
1/8 teaspoon pepper
¼ teaspoon dry mustard
1 cup milk
1 ½ cups cooked chicken, cubed
½ cut ham, cooked and cubed
4 slices Swiss cheese
1 can of crescent roll dough
1 tablespoon melted butter of margarine

Melt butter in saucepan over low heat and blend in flour, salt, pepper and dry mustard. Cook over low heat, stirring until mixture is smooth and bubbly. Stir in milk, blending until smooth. Let boil gently for about 1 minute and remove from heat. Add chicken and ham to sauce mixture. Spread in to an 8 x 8 pan that has been lightly greased and cover with sliced cheese. Spread crescent roll dough over the chicken mixture, making sure to cover completely. Pour melted butter or margarine over the crescent roll dough and bake for 20 to 25 minutes, or until filling is hot and bubbly and top is golden brown.