Cook vegetables in boiling water for 5 minutes. Drain, reserving 1 cup of liquid. Place vegetables in a casserole dish. Set aside.
In a heavy saucepan melt 1/4 cup butter. Stir in flour and cook, stirring for 3 minutes. Gradually stir in reserved liquid, then the cream. Cook, stirring constantly until liquid comes to a boil. Add mustard, salt and pepper.
Pour sauce over vegetables.
Preheat oven to 375 F. In a small saucepan, melt 2 tablespoons of butter. Add bread crumbs and mix until combined. Sprinkle on top of vegetables. Bake for 30 minutes.