Wash the beans well and put them in a large stockpot. Add water to the beans to cover by 2 inches and set over high heat. Bring to a boil for 2 minutes, remove from the heat, cover and let stand 1 hour.*
Preheat the oven to 375 degrees F.
Put the duck sausage on a baking sheet and place it in the oven for 15 to 20 minutes. Remove and let cool. The sausage will not be fully cooked through.
Add the whole onion, whole carrot, 2 of the thyme sprigs and 3 of the bay leaves to the beans. Add more water to the pot to cover again by 2 inches. Bring to a boil, lower the heat and let simmer until the beans are mostly tender but with still a little bite to them, about 50 to 60 minutes. The beans will have soaked up all most all of the liquid you cooked them in.
Meanwhile, pour the olive oil into a large skillet and place over medium heat. Add the bacon and cook stirring every now and then until crispy, about 2 to 3 minutes. Using a slotted spoon remove the crispy bacon pieces to a paper towel lined plate and reserve. To the same skillet, add the diced onion, sliced carrots and garlic and sweat the mixture for 20 minutes, until the onion begins to turn translucent.
Slice the duck sausage on the bias into 1/2-inch thick pieces and add them to the vegetable mix. Add the remaining bay leaves, thyme sprigs and sliced kielbasa and cook, stirring, for 5 minutes. Next add the wine, beef broth, tomato paste and salt and pepper. Raise the heat to high, bringing the mixture to a boil. Stir well to dissolve the tomato paste and lower the heat. Allow to simmer for 5 minutes.
Remove the whole onion and carrot from the beans, add the vegetable sausage mixture to the stockpot and return to a low heat. Stir well and cover. Let the cassoulet simmer for 15 to 20 minutes, or until most of the wine mixture has been absorbed by the beans. Spoon into a casserole dish, sprinkle the top of each serving with some of the reserved crispy bacon and serve with a crusty baguette on the side.
*This is the quick soak method. The beans can also be left to soak overnight in cold water.
Recipe courtesy of Dan Smith and Steve McDonagh