Cowboy Bean Casserole

5 ounces diced ham
1 ounce butter or margarine
1 clove garlic, crushed
1 1 pound can baked beans, drained
1 1 pound can red kidney beans, drained
1 1pound can butter beans, drained
1 tablespoon brown sugar
1 tablespoon mustard with horseradish
4 fluid ounces tomato ketchup
3 tablespoons vinegar
salt and pepper
1 medium onion, sliced

Brown ham in butter or margarine.
Combine garlic, beans, ham, mustard and seasonings.
Pour into a greased casserole.
Top with onion slices.
Cook in moderate oven (350F Mark 4) for 45 to 60 minutes.
Serves 6.