Heat 1" water to boiling in 2-quart saucepan. Add leeks. Cover and cook over medium heat about 5 minutes or until crisp-tender; drain. Heat oven to 325. Prepare 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. Stir in cheese until melted. Stir in leeks. Pour into prepared casserole. Sprinkle with crumb topping. Bake uncovered about 25 minutes, or until heated through.

Topping: Simply mix together the ingredients until the bread crumbs are moistened.

supposed to be a low-fat recipe, and I suppose it would be okay the way it is written. Being personally unable to follow a recipe exactly, I use butter, extra cheese, extra pepper and usually make twice the amount of topping.