How to Make It
In a large saucepan, cover the beans with the stock and bring to a boil. Reduce the heat to moderately low and simmer until the beans are just tender, about 1 hour. Drain the beans, reserving the stock. Return the stock to the saucepan and boil over high heat until reduced to 4 cups, about 7 minutes.
Meanwhile, melt the butter in a large skillet. Working in 2 batches, season the rib meat with salt and pepper and cook over moderately high heat until browned all over, about 4 minutes per batch. Transfer to a platter. Add the bacon to the skillet and cook until the fat is rendered and the meat begins to crisp, about 5 minutes. Transfer the bacon to the platter. Add the andouille to the skillet and cook over moderately high heat until lightly browned, about 3 minutes. Transfer to the platter. Add the reserved rib bones to the skillet and cook over moderately high heat until lightly browned, about 2 minutes per side. Add to the platter.
Add the onion, carrots and garlic to the skillet and cook over moderate heat, stirring occasionally, until softened and golden, about 8 minutes. Add the chopped tomatoes, thyme and bay leaf and cook, stirring until the tomatoes release their juices, about 3 minutes. Return the rib meat, bacon and andouille to the skillet; stir until heated through.
Preheat the oven to 300°. Scrape the meat and vegetables into a large glass or ceramic baking dish. Nestle in the rib bones and top with the white beans and the reduced stock. Bake the cassoulet for 1 hour and 30 minutes, or until bubbling and the beans on top are crisp. Let stand for 15 minutes. Pick out the bay leaf and serve.