In a large saucepan, melt 2 tablespoons butter. Stir in flour and salt. Add milk and stir until bubbly. Add cheese, stir until the cheese is melted. Stir in potatoes and heat thoroughly.

Pour half of the mixture into a 10x6 baking dish.

Cook broccoli according to package instructions; drain well. Layer broccoli over the potatoes in the baking dish. Pour remaining potato mixture over the broccoli. Sprinkle the bread crumbs and 1 Tbsp melted butter over the top of the casserole.

Bake for 20-35 minutes; or until bubbly and browned lightly.