Cook the beans in unsalted water for 1 hour. Drain and reserve the liquid. Use a heavy casserole with a lid and place the onions at the bottom.
Cover with the beans. Mix the sugar, molasses, mustard, salt and a good amount of black pepper with 1 cup - 250ml) of the bean liquid.
Pour over the beans, stir gently and cover the casserole. Bake for at least 3 hours at 250° F adding more liquid if too dry. If the dish is too liquid, remove the lid for the last 30 minutes of cooking.Servings: