Step 1
Start by heating your oven to 350°F (175°C). In a large casserole dish, mix together the black beans, kidney beans, butter beans, lima beans, brown sugar, chopped onion, tomato sauce, celery, vinegar, and mustard powder until everything is well combined. Cover the dish tightly with aluminum foil and pop it into the oven. Let it bake for about an hour, giving the flavors plenty of time to meld together. When it’s done, take it out and give it a good stir before serving.



