Cook the bacon, onion, and garlic in a skillet over medium heat until the bacon is cooked and the onion has softened. Drain the mixture well.
Place the bacon mixture in a large bowl with the butter beans, lima beans, pork and beans, red kidney beans, and chickpeas. Stir gently to combine.
Transfer the bean mixture to a casserole dish.
In a separate bowl, combine the ketchup, molasses, brown sugar, Worcestershire sauce, prepared mustard, and ground black pepper. Pour the sauce over the beans and stir slightly to distribute it throughout the casserole.
Bake for 1 hour, or until the beans are hot and bubbly and the sauce has thickened. Serve warm.
Recipe Tips
The two-stage baking method matters here. Covering the dish during the first 45 minutes traps steam and allows the beans to absorb the sauce without drying out. The final 15 minutes concentrate the sauce and create the slightly caramelized top layer that gives the dish its texture contrast.
If the sauce looks thin when you remove the foil, that is expected. It will thicken significantly during the uncovered bake and continue to set during the resting period.
For a smokier result, use thick-cut bacon and cook it until just past golden rather than fully crispy. The fat renders more completely, and the slightly chewier bacon pieces hold up better through the hour-long bake.
This casserole tastes better the second day. If making it for a gathering, consider baking it the night before, refrigerating overnight, and reheating covered at 325 degrees F for 30 minutes.