Place the beans in a large bowl and cover with cold water by 2.5cm and cover with plastic wrap. Refrigerate overnight. Drain and rinse the beans and then drain again.
Place the beans in large pot with 2.2L water, the onion, bay leaf, and peppercorns. Bring to a boil, then lower the heat and simmer for about 50 minutes, or until tender. A good test is to scoop up several beans in a spoon and blow on them: if the skin starts to peel off, they're done. Drain the beans, reserving the cooking liquid.
Preheat the oven to 110°C/gas mark 1.
In a small saucepan, whisk together the maple syrup, brown sugar, ketchup, chili paste, ginger, salt, and 375ml of the cooking liquid, still reserving the remaining liquid. Bring to a simmer and cook over medium heat for 6 minutes.
Transfer the beans to a medium casserole dish. Push half the bacon into the beans and place the rest on the top. Pour the maple syrup sauce over the beans. Place the lid on top and bake for 6 to 8 hours. Check occasionally; if the beans are too dry, add 125ml more of the cooking liquid. If you like, you can remove the lid for the last 30 minutes to thicken the sauce. Discard the bay leaf. Serve hot.