PREHEAT oven to 350º F.
MICROWAVE potatoes and water in covered, medium, microwave-safe casserole dish on HIGH (100%) power for 9 minutes; drain. Return to dish; top with frozen vegetables.
MELT 2 tablespoons butter in small saucepan over medium heat. Stir in flour; cook, stirring constantly, for 30 seconds. Gradually stir in evaporated milk, bouillon and pepper; cook, stirring occasionally, for 3 to 4 minutes or until bouillon is dissolved and sauce is slightly thickened. Pour sauce over vegetables.
MICROWAVE remaining butter in small, microwave-safe bowl on HIGH (100%) power for 10 to 20 seconds or until melted. Stir in bread crumbs until well combined. Sprinkle over vegetables; cover.
BAKE for 30 minutes. Uncover; bake for an additional 10 minutes or until top is golden brown.