Line four 8x8x2-inch baking pans with heat-resistant freezer wrap. Allow enough extra wrap to fold over top. Use one pan for each six servings or one-fourth of the recipe. Do not line pans for food to be served without freezing.
Melt fat. Stir in flour, salt, pepper, and onion. Add broth slowly. Cook until thickened, stirring constantly. Mix hot mixture with chicken, corn, cheese, and pimentos. Pour one-forth of mixture into each baking pan. Spread well to avoid air pockets.
TO SERVE WITHOUT FREEZING: Preheat oven to 350=B0 F. (moderate). For each pan to be baked right away, mix 1/4 cup fine dry bread crumbs with 1 tablespoon melted butter or margarine. Sprinkle over chicken mixture in baking pan. Bake 45 minutes or until crumbs are lightly browned.
TO FREEZE: Cool for 30 minutes at room temperature. Complete wrapping by pulling paper up over top of food. Put edges of wrap together and fold several times so paper lies directly on top of food. Fold ends of freezer wrap over the top and seal with freezer tape. Label with name of food, date of freezing, and last date the food should be used for best eating quality (about 6 months). Freeze immediately for 10 to 12 hours before removing packages from the pans.
TO HEAT FROZEN FOOD: Preheat oven to 350=B0 F. (moderate). Remove freezer wrap. Place food in baking pan. For each pan to be baked, mix 1/4 cup fine dry bread crumbs with 1 tablespoon melted butter or margarine. Sprinkle over chicken mixture in baking pan. Bake 1 1/4 hours or until crumbs are lightly browned, and center is hot.