1. For the lamb, combine paprika, thyme, rosemary, and half of the garlic with 11⁄2 tsp salt and 1⁄2 tsp ground black pepper. Rub the mixture over the lamb shanks, cover, and refrigerate for at least 4 hours or overnight.

2. Heat oven to 160°C. Heat oil in a large casserole over medium-high heat. Add shanks, and brown (3-5 minutes per side; the more color you get on the meat, the richer the sauce). Transfer meat to a plate as it browns. If casserole looks dry, drizzle in a little more oil. Add onion, carrots, celery, remaining garlic, and a pinch of salt and sauté until vegetables are tender and golden (5-7 minutes). Add tomato paste and harissa and cook until pastes darken (30 seconds-1 minute). Add wine and cook until reduced by half (3-5 minutes). Add stock and bring to a simmer. Return the lamb and any juices to the pot, cover, and braise in the oven, turning every 1/2 hr, until meat is very tender (11⁄2-2 hours). When meat is cool enough to handle, coarsely shred meat.

3. Meanwhile, drain beans and place in a pot with enough water to cover by 5cm;
add bouquet garni and 2 tsp salt. Bring to a simmer and cook for 30 mins. Add sausage
to beans and poach for 15 minutes. Transfer sausage to a cutting board to cool slightly. Continue to cook beans until tender (15 minutes and up to 2 hours, depending upon what kind you used; If water level gets low, add boiling water to the pot.) Drain beans in a colander set over a bowl to catch the liquid, and discard herbs. Reserve cooking liquid.

4. When lamb is cool enough to handle, tear meat and put it in a bowl. Discard bones. Scoop out vegetables from the pot and add them to the lamb. Taste liquid left in the pot. If it tastes bland and seems thin and watery, simmer until it thickens slightly, then season to taste with salt and pepper. Transfer liquid to a measuring cup and spoon fat off the top. You should have between 1-11⁄2 cups liquid. Reserve the liquid. Reserve the casserole for baking the cassoulet.

5. To finish the beans, heat oil in a large frying pan over medium-high heat until it shimmers, add onion, half the garlic, the pepper, and a pinch of salt. Sauté until onion is translucent, about 4 minutes.

6. Dice reserved lamb sausage and add to the pan. Sauté until sausage and onions are golden (5-10 minutes). Add tomato purée and simmer until oil separates and sauce reduces, about 10 minutes. Add drained beans and stock, and simmer, stirring occasionally, until the beans are moist and very soupy (12-15 minutes). Add some reserved bean cooking liquid if mixture dries out at any point. Stir in the remaining garlic, lemon zest, and parsley. Season to taste.

7. Increase oven to 180°C. Spoon half the beans into the casserole, top with lamb and vegetables, and cover with remaining beans. Pour reserved lamb liquid around edges until it reaches the top. If there’s not enough lamb liquid, add some reserved bean liquid.

8. For topping, mix butter, rosemary, garlic, zest, and 1⁄4 tsp salt in a bowl. Add crumbs and mix, making sure butter is distributed. Sprinkle mixture evenly on top of the beans in the pot. Bake until crust is lightly browned, about 30 minutes. Use the a large spoon to lightly crack the crust; the liquid will bubble up. Spoon this liquid all over the top of the crust. Return to the oven and bake for 30 minutes to 1 hour more, cracking the crust and drizzling with the bean liquid every 20 minutes or so, until crust is well-browned and the liquid is bubbling. (The total baking time should be 11⁄4 to 11⁄2 hours.) Cool slightly, then serve.