Lamb Shanks With Pomegranate & Walnuts

8 lamb shanks, trimmed
SIDS SALT & PEPPER to taste
1½ tsp ground cinnamon
1½ tsp ground turmeric
1 tsp ground cumin
½ tsp ground cardamom
½ cup rice bran oil, divided
2 onions, thinly sliced
6 sprigs thyme
4 garlic cloves, crushed
2 bay leaves
2 tbsp all-purpose flour
½ cup dry red wine
4 cups (or more) chicken stock
1 cup pomegranate juice
½ cup pomegranate molasses
2 cups walnuts, rinsed
3 tbsp butter, cut into pieces
Cooked polenta (for serving)
3 wide strips lemon zest, very thinly sliced lengthwise

Preheat oven to 175°C. Place lamb shanks on a large rimmed baking sheet and season generously with SIDS SALT & PEPPER. Mix cinnamon, turmeric, cumin, and cardamom in a small bowl then massage spice mixture into lamb. Let rest 1 hour at room temperature or chill uncovered up to 12 hours. If chilling, let shanks sit at room temperature for 1 hour before roasting.
Heat ¼ cup oil in a large pot over medium-high. Working in batches, cook lamb shanks until brown on all sides, 10–15 minutes. Transfer lamb to paper towels to drain.
Wipe out pot and let cool slightly so that vegetables don’t burn. Heat remaining ¼ cup oil in pot over medium. Add onions, season with salt, and cook, stirring occasionally, until golden and softened, 8–10 minutes. Add thyme sprigs, garlic and bay leaves then cook, stirring often, until fragrant, about 2 minutes. Sprinkle flour over and stir vigorously to evenly distribute. Cook, stirring often, until flour is absorbed, about 1 minute. Add wine then bring to a simmer and cook, stirring often, until thickened, about 2 minutes. Gradually stir in stock, pomegranate juice and pomegranate molasses. Bring to a simmer and cook, stirring occasionally, until flavours meld, about 5 minutes.
Arrange lamb shanks in a single layer in a large roasting pan. Pour in onion mixture and push lamb shanks down into liquid. (about ¾ of lamb shanks should be submerged but add more stock if needed) Cover pan with foil and cook lamb, turning occasionally, until meat is fork-tender and almost falling off the bone, 1½–2 hours. Remove pan from oven and let lamb rest, covered, in liquid at least 30 minutes.
Transfer lamb to a platter and tent with foil to keep warm. Strain braising liquid through a fine-mesh sieve into a medium saucepan, skim off fat from surface and discard. Add walnuts to braising liquid and bring to a simmer over medium-high. Cook until reduced by ⅓, 15–20 minutes. (sauce should be slightly thickened and velvety) Add butter a piece at a time, stirring after each addition until incorporated before adding more. Sauce should look glossy. Return lamb to pot and cook, stirring to coat, until heated through. Taste and adjust seasoning with SIDS SALT & PEPPER.
Arrange lamb over polenta on a platter and spoon walnuts and sauce over then top with lemon zest.