Preparation / Directions:
Cook frozen mixed vegetables in a medium saucepan according to package directions. Drain well and set aside. Melt 1 tablespoon butter in a heavy saucepan over low heat; add flour and mustard, stirring until smooth. Cook 1 minute, stirring constantly. Gradually add milk; cook over medium heat, stirring constantly, until thickened and bubbly. Add cheese, Worcestershire sauce, salt and pepper; stir until cheese melts. Stir cheese sauce and onion into vegetables; mix well. Spoon mixture into a greased 1-quart casserole. Combine bread crumbs and melted butter; sprinkle over vegetable mixture. Bake, uncovered, at 375 degrees for 20 minutes.