1. Cover beans with water and soak overnight. Drain and put into a large
heavy casserole, preferably enameled cast-iron, with ventrèche, garlic, onions,
carrot and bouquet garni. Cover with the 10 cups of water and bring to a boil.
Simmer over low heat, stirring often, until beans are barely tender, about 1
hour.
2. Drain beans, (save some of the liquid), discard onions and bouquet garni. Cut
ventrèche into 1/2 inch squares.
3. Season beans with 1 teaspoon salt and several grindings of pepper.
4. Preheat oven to 325° F.
5. Place half of the bean mixture in casserole. Add duck legs, browned duck
sausages, chopped ventrèche and garlic sausage slices, then cover with remaining
beans.
6. Mix tomato paste into dissolved demi-glace, then pour over bean mixture.
Add some of the bean liquid if needed.
7. Drizzle duck fat over top.
8. Cover and bake until hot and bubbling, about 2 hours, checking occasionally
to time to make sure it is not drying out (add some reserved water). Mix the
beans around once or twice.
9. Increase oven temperature to 400° F. Uncover casserole and bake until top is
browned, about 20 minutes. Remove from oven and serve.