How to Make It
Preheat the oven to 325°. In a large skillet, heat 1 tablespoon of the olive oil. Season the lamb shanks with salt and pepper. Add 3 of the shanks and cook over moderately high heat until browned all over, about 10 minutes. Transfer to a large roasting pan. Repeat with 1 tablespoon of the olive oil and the 3 remaining lamb shanks.
Pour off the skillet oil. Add the wine and boil for 1 minute, scraping up any browned bits; pour the wine into the roasting pan with the lamb. Add the stock, coarsely chopped onions, celery, carrot, thyme and bay leaves to the roasting pan and bring to a boil over high heat. Cover with foil and braise the lamb shanks in the oven for 2 1/2 hours, turning them once, until the meat is very tender. Remove the foil. Let cool slightly.
Meanwhile, in a medium skillet, heat 2 tablespoons of the olive oil. Add the garlic, finely chopped onion, mustard seeds and cumin seeds and cook over moderate heat until the onion is golden, about 7 minutes. Add the tomatoes and cook until reduced to 2/3 cup, about 4 minutes. Season the tomato sofrito with salt and pepper.
Increase the oven temperature to 400°. On each of 2 large rimmed baking sheets, toss the squash with 1 tablespoon of the olive oil. Season with salt and pepper and arrange in an even layer. Roast the squash for 45 minutes, or until tender. On another large rimmed baking sheet, toss the broccoli with the remaining 1 tablespoon of olive oil; season with salt and pepper. Roast for 25 minutes, or until lightly browned and just tender.
Meanwhile, transfer the lamb shanks to a work surface and cover to keep warm. Strain the braising liquid into a large saucepan and skim off the fat. Add the chickpeas, tomato sofrito and lamb shanks to the braising liquid, cover and simmer over low heat for 5 minutes. Season with salt. Stir in the roasted squash and broccoli.
Cook the couscous according to package instructions then toss with the butter and season with salt. Keep covered.
Set the lamb shanks in shallow bowls and spoon the couscous alongside. Ladle the vegetable stew on top and pass the Spicy Cilantro Pesto at the table.