4 cups dried navy or pea beans (about 2 pounds)
2 whole cloves
1 medium onion
1 teaspoon baking soda
1 pound slab bacon (rind removed), cut into 1/4-inch cubes
1 1/2 cups dark molasses (not blackstrap)
2 teaspoons ground mustard
2 tablespoons kosher salt
Freshly ground black pepper to taste
2 tablespoons dark rum
Place the beans in a large bowl with enough water to cover by 3 inches and soak overnight.
Heat the oven to 275°F and place a rack in the lower third.
Drain the beans, place in a large (6-quart) Dutch oven or a large, heavy-bottomed pot, and add cold water to cover by 1 inch. Press the cloves into the onion and add the onion and baking soda to the pot; stir to combine.
On the stovetop, bring the beans just to a boil over high heat. Reduce the heat to low, skim off the foam, and simmer for 15 minutes. Add the remaining ingredients and stir until combined.
Place the pot in the oven and bake slowly until the beans are tender, 5 to 6 hours. Add a little water if necessary. Allow the top of the beans to crust slightly during the final 30 minutes of baking. Serve hot.