Soak the Dried Navy Beans overnight in plenty of cold Water so they are covered by 2 inches; if short on time, use a quick-soak by boiling for 2 minutes, removing from heat, covering, and letting sit 1 hour before draining.
Drain and rinse the soaked beans and set aside.
Preheat the oven to 300°F (150°C).
Cut the Salt Pork into small dice. In a heavy ovenproof pot or Dutch oven, cook the salt pork over medium heat until much of the fat has rendered and the pieces are beginning to brown, about 5–8 minutes.
Add the chopped Yellow Onion to the pork and cook until softened and translucent, about 5 minutes, scraping up any browned bits.
Stir in the drained beans, enough Water to cover the beans by about an inch, the Unsulfured Molasses, and the Light Brown Sugar. Add the Dry Mustard Powder and give everything a good stir to combine.
Bring the pot to a gentle simmer on the stovetop, then cover and transfer to the preheated oven.
Bake low and slow for 3 to 4 hours, checking every hour after the first to stir and add a little Water if the beans look dry; the beans are done when tender and the sauce has thickened to a glossy, spoonable consistency.
Near the end of cooking, season to taste with Kosher Salt and freshly ground Black Pepper; remember that the salt pork contributes salt, so taste before adding much salt.
If you like a slightly caramelized top, uncover for the final 20–30 minutes of baking to allow the sauce to reduce and darken.
Let the beans rest 10–15 minutes off the heat before serving so the sauce sets slightly; serve warm as a hearty side or main.
