Melt butter in skillet over medium-low heat; add ham and sauté until browned. Sprinkle with a little salt and pepper; remove from pan.
Add onion and garlic to the skillet; sauté for about 5 minutes. Add sugar, mustard, beans, ketchup, and vinegar. Mix well. Pour into a 2-quart casserole, arranging ham on top. Cover and bake at 350° for 30 minutes. Serves 4. Serve with cornbread or crusty French bread.