Place dry beans in stock pot, cover with cold water and soak overnight. Drain and rinse.
Preheat oven to 300 F. Dice onion and bacon, and place in large Dutch oven along with brown sugar, molasses, tomato paste, mustard, salt and pepper.
Add 4 cups warm water and stir until sugar dissolves.
Add beans, and bring to a boil.
Cover and place in oven. Bake for 4 hours. Add sausages and bake another 1 hour. Add more water if too dry, 1/2 cup at a time.