4 medium leeks with tops (about 2 pounds), cut into 1/2-inch pieces
Crumb Topping
1 Tbs margarine
1 Tbs plus
1 tsp all-purpose flour
1/4 tsp salt
1 dash pepper
2/3 cup skim milk
1/2 cup shredded Gruyere cheese (2 ounces)
CRUMB TOPPING
2 Tbs dry bread crumbs
1 tsp margarine, melted


Heat 1 inch water to boiling. Add leeks. Cover and cook over medium heat about 5 minutes or until crisp-tender; drain. Heat oven to 325 degrees. Prepare Crumb Topping. Spray shallow 1-quart casserole with nonstick cooking spray. Heat margarine in 2-quart saucepan over low heat. Stir in flour, salt and pepper. Cook over low heat, stirring constantly, until margarine is absorbed; remove from heat. Gradually stir in milk. Heat to boiling, stirring constantly. Boil and stir 1 minute. Stir in cheese until melted. Stir in leeks. Pour into casserole. Sprinkle with Crumb Topping. Bake uncovered about 25 minutes or until heated through.
CRUMB TOPPING Mix all ingredients.