Rinse the dried beans under cold water, removing any stones or debris. Place beans in a large bowl and cover with at least 4 cups of water. Soak overnight (8–12 hours) or use the quick-soak method: bring beans and water to a boil for 2 minutes, remove from heat, cover and let sit 1 hour. Drain and rinse after soaking.

Cook beans

Place soaked, drained beans in a large pot. Add 4 cups fresh water and the bay leaf. Bring to a gentle boil, then reduce heat and simmer, partially covered, until beans are just tender but not falling apart, 45–60 minutes. During the last 10 minutes of cooking, add 1 tsp salt to the pot. Drain, reserving about 1 cup of the cooking liquid; discard bay leaf. Adjust salt to taste (you may add up to the full 1.5 tsp total if needed).

Sauce

Cook aromatics and bacon

Preheat the oven to 325°F (160°C). In a medium skillet over medium heat, add the diced bacon and cook until fat renders and pieces are crisp (about 6–8 minutes). Remove with a slotted spoon to a paper towel-lined plate, leaving most of the fat in the skillet. Add the chopped onion to the bacon fat and cook until translucent and lightly golden, about 6–8 minutes. Add minced garlic and cook 30–45 seconds more until fragrant.

Make sauce

Stir into the onion mixture the ketchup, brown sugar, molasses, Dijon mustard, apple cider vinegar, Worcestershire sauce, smoked paprika and black pepper. Cook, stirring, for 2–3 minutes to meld flavors and dissolve the sugar. If the sauce looks too thick, add up to 1/2 cup water to reach a spoonable consistency. Taste and adjust seasoning — add a pinch more salt or sugar if desired.

Assemble & Bake

Combine beans and sauce

In a 2–3 quart ovenproof casserole or Dutch oven, combine the cooked beans, the prepared sauce, and the reserved bean cooking liquid (start with 1/2 cup and add more if beans look dry). Stir in the cooked bacon (reserve a tablespoon for topping if desired). Dot the top with the butter.

Bake

Cover the dish with a lid or foil and bake in the preheated 325°F (160°C) oven for 45 minutes. Remove the lid/foil and bake uncovered another 20–30 minutes, until sauce is thickened and bubbling and beans are fully tender. If you like a thicker glaze, bake an additional 10–15 minutes, watching to prevent burning. Total oven time ~65–75 minutes.

Finish and serve

Remove from oven and let rest 10 minutes. Taste and adjust seasonings (add salt, pepper, or a splash of vinegar for brightness). Sprinkle with reserved bacon and chopped parsley if using. Serve warm as a side.