Method
Place the beans into a large bowl and cover with plenty of fresh cold water. Leave them to soak for 6–8 hours or overnight.
Heat the oven to 180°C.
Set a large heavy casserole pan over a medium heat. Add the olive oil, then tip in the smoked bacon lardons. Let them fry gently until they begin to crisp around the edges and release their fat.Add the sliced onions, celery, garlic and chilli. Stir well and cook, stirring now and then, for 10–12 minutes until the vegetables have softened nicely.
Crush the plum tomatoes and add them to the pan along with the brown sugar, mustard, bay leaves, thyme and rosemary. Bring everything up to a gentle simmer. Drain the beans and stir them through.
Pour over the stock, season generously with salt and pepper, and bring the mixture back to a simmer. Fit the lid on the pan and slide it into the centre of the oven for 1½ hours. Check occasionally — if the beans look dry, add a splash of water.
Remove the pan from the oven and taste for seasoning. The beans should be rich, soft and melt-in-the-mouth tender. Bring the pot straight to the table and serve with warm bread, a green salad and a glass or two of red wine.