Heat oven to 350°F. In 3-quart saucepan, melt 4 tablespoons of the butter over medium heat. Stir in flour and pepper; cook, stirring constantly, until mixture is smooth and bubbly. Gradually add broth and milk, cooking and stirring about 4 minutes or until mixture is bubbly and thickened.
Stir in cheese, mixed vegetables and broccoli; pour into ungreased 2 1/2- to 3-quart casserole.
In medium microwavable bowl, microwave remaining 2 tablespoons butter on High 20 to 30 seconds or until melted. Stir in bread crumbs until coated; sprinkle over vegetable mixture.
Bake 25 to 30 minutes or until edges are bubbly.