Soak the navy beans in 4 cups of water overnight.
Drain and rinse the beans and then place in a large saucepan or stockpot.
Add 4 cups of water and bring to a boil over high heat. Boil for 15-20 minutes, then drain - reserving the cooking water.
While the beans are cooking, combine the sauce ingredients in a large bowl.
When the beans are done, add them to the sauce and stir to coat completely.
Preheat oven to 325F.
In a casserole dish, layer the beans with the bacon and onions: 1/2 of the chopped onion, 3-4 strips of bacon, 2 cups of beans, then remaining 1/2 onion, remaining 3-4 strips bacon and remaining 2 cups beans.
Pour enough of the bean cooking water over the beans to cover in about 1/2” of water.
Place the casserole dish in the oven, uncovered, and bake for 3-4 hours until all of the water appears to be absorbed.
Stir well and serve.