Place beans in a large bowl or pot. Cover with water by 2 inches. Cover and let stand overnight. Drain and rinse the beans.
Place the beans in a large pot and cover with fresh water (about 1 quart). Bring to a boil, then reduce the heat so that the liquid is at a gentle simmer. Cover the pot and simmer the beans until tender, about 1 ½ hours. Drain and rinse.
Preheat oven to 325° F.
In a large Dutch oven over medium heat, cook bacon until crisp, about 7-8 minutes. Use a slotted spoon to remove the bacon to a paper towel-lined plate; reserve 2 tablespoons of drippings in the pot (discard any excess).
Add the onion to the drippings in the pot and season with a pinch of salt. Cook over medium-high heat until the onion softens, about 5 minutes.
Stir in the beans, bacon, ketchup, molasses, vinegar, dry mustard, ½ teaspoon kosher salt and ¼ teaspoon of black pepper. Add enough of the broth to cover the beans (if necessary, add water as well to cover the beans).
Cover and bake until the beans are tender, about 2 hours, stirring the pot halfway through.
Taste and season with additional salt and pepper, if necessary. Garnish with chopped fresh parsley, chives or sliced green onions.