03Meanwhile, melt the butter with the olive oil in a pan over high heat. Reduce heat to medium, add the celery, the carrot, the onion, the remaining bay leaf and the cloves, and saute until the vegetables are softened, about 10 minutes.04Squeeze the juice from the tomato into the pan before adding the rest of it in one piece. Cook 2 more minutes, remove from heat and remove the cloves and bay leaf. Combine with the beans.05Crowd the sausages into a small pan, and cook over medium-low heat, rotating frequently, until brown in the center, about 45 minutes. Break some of the larger pieces of sausage with a spatula before adding them and their juices to the bean mixture, adjusting with salt and about 1 cup of the reserved bean cooking liquid. Serve with polenta.