Cover the beans with cold water and soak overnight. Alternately place beans in a large pot with 6 cups (1.5 L) water, cover and bring to a boil. Boil 5 minutes, remove from heat and let stand for 1 hour. Drain and discard water, then rinse.
Place drained beans in a large pot with 6 cups (1.5 L) water, after boiling for 5 minutes, reduce heat and simmer until beans are tender, about 30 minutes. To see whether a bean is tender, simply remove it from the boiling water and blow on it. If the skin cracks and peels back, it’s ready. Drain, reserving 1 cup (250 mL) of the liquid. Transfer to a slow cooker, bean pot or casserole dish with a lid. Combine the reserved water with mustard, brown sugar, molasses, salt, pepper, pork or bacon and vinegar.
Cook on high in a slow cooker or at 300’F (150’C) in the oven. Beans done in a slow cooker will take about 6 hours; in the oven from 4 to 6 hours. Add water during cooking as needed to keep beans moist.