Preheat oven to 350. Lightly grease a 13 x 9 baking dish; set aside.
Cook cabbage in boiling salted water until tender. Drain well; keep hot and set aside.
Meanwhile, melt the 3 tbsp butter in a saucepan. Saute the onion and garlic til soft but not browned.
Stir the flour into the butter/onions/garlic until smooth.
Gradually stir in the milk and keep stirring until mixture thickens.
Add the mustard powder, salt, pepper and cheese. Stir until cheese is melted and sauce is smooth.
Mix the cooked cabbage with the sauce and pour into the prepared baking dish.
Mix the melted butter and cracker crumbs and sprinkle over top.
Sprinkle with paprika.
Bake at 350 for 25-30 minutes.
