Preheat oven to 350°F.
Heat butter and bacon in a medium saucepan over medium heat. Add onion and bell pepper; cook 4 minutes, stirring occasionally. Add corn syrup and brown sugar and cook 1 minute. Stir in beans and mustard; bring to boil and boil for 1 minute.
Pour into lightly greased 8-inch square baking dish. Bake 30 minutes or until hot and bubbly.
Southwestern Sweet Black Beans:
Stir in 3 tablespoons chopped green chilies and 2 tablespoons chopped cilantro along with beans. Omit mustard. Bake as directed.