Preheat the oven to 160°C / 300°F / Gas Mark 2.
Place the duck legs on a baking tray and roast in the oven for 1½ hours.
Bean stock :
Cut the onion and garlic in half. Put in a large saucepan with the thyme, rosemary, carrot and beans covering with cold water. Bring to the boil and simmer for 10 minutes.
Dice the pork meat and roll the pork skin into a sausage shape, tying with string in three places. Add the rolled skin and diced pork to the bean stock.
Reduce the heat and cook for 1 hour, removing any scum as it appears on the surface.
Put the diced carrots and finely chopped tomatoes into a large bowl - this will be the bits bowl.
Heat 2 tbsp of the duck fat in a large ovenproof casserole dish. Lightly fry the diced onions and chopped garlic until softened. Then remove with a slotted spoon and add to the bits bowl.
Lightly fry the sausages in the casserole dish until golden brown. Remove and cut each sausage into three pieces. Add them to the bits bowl.
Continue with the bean stock
Drain the bean stock, setting the stock aside for later. Pour all the other ingredients into a large roasting tray. Pick out the pork meat and rolled skin. Discard the carrot, onion, herbs and garlic.
To make the cassoulet
Put the pork and rolled skin into the casserole dish and lightly fry until golden brown. Remove the pork with a slotted spoon and add to the bits bowl. Remove the pork skin, unroll it and put it back into the base of the casserole dish, skin side down.
Pour half the beans over the pork skin. Add the duck legs and all the meat and vegetables from the bits bowl.
Spread the remaining beans over the mixture.
Pour in the bean stock, filling to the level of the beans. Add some boiling water if necessary.
Put the dish in the preheated oven and cook without a lid for 2 hours.
After 2 hours, a dry crust will have formed on the beans. Break it up and mix into the top layer of beans. Sprinkle the breadcrumbs over the top and drizzle the remaining duck fat on top. Cook for a further 10 minutes or until the breadcrumbs are golden brown.
Serve with crusty bread.
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