Step 1Place the beans in a bowl; cover by 3 inches with cold water. Soak 8 hours. Drain. Cook in boiling water 30 minutes, then drain.
Step 2In a large, heavy saucepan, melt the fat over medium-high heat. Fry the sausages until browned. Remove from the pan, reduce heat to medium and add the onion. Cook until golden, 5 minutes. Add the bacon, beans, bouquet garni, garlic, and season with salt and pepper. Add cold water to cover. Cook uncovered, 1 1/2 hours. Check the seasoning. Add the carrots and tomatoes. Cook 30 minutes, then set sausages on top, check seasoning, and cook until the water is just under the beans and thick, 30 minutes to 1 hour.