Soak the beans overnight in water to cover. Drain. Rinse. Add water to cover and the baking soda. Bring to a boil. Reduce the heat. Simmer for 10 minutes. Drain. Rinse. Preheat the oven to 300 degrees.
Place the onion in the bottom of a 3 quart ovenproof casserole. Add half the bacon, add the beans, and top with remaining bacon. Mix the sugar, molasses, mustard, salt, and pepper together. Pour over the beans. Add just enough water to barely cover. Do not stir. Cover. Bake for six hours, you may need to add a little water, be careful not to get the beans to wet. Yield: 16 servings