Ingredients

• 2 cups fresh basil leaves
• 2 tablespoons olive oil
• 1 3-pound boneless lamb shoulder roast, tied (a butcher can do this)
• Kosher salt, freshly ground pepper
• 4 sprigs thyme
• 1 small shallot, finely chopped
• 1 garlic clove, finely grated
• 1 cup coarse polenta
• 1 cup heavy cream
• 3 cups (or more) low-sodium chicken broth
• Kosher salt, freshly ground pepper
• 1/3 cup sugar
• 1/3 cup unseasoned rice vinegar
• 1/2 teaspoon hot chili paste (such as sambal oelek)
• 1 teaspoon kosher salt plus more
• 2 leeks, white and pale-green parts only, halved lengthwise, sliced crosswise 1/4" thick, divided
• 3 ounces thick-cut bacon, sliced crosswise 1/4" thick
• 1 14-ounce can cannellini beans, rinsed
• Freshly ground black pepper
• 3/4 cup fresh flat-leaf parsley leaves
• 1/2 cup fresh cilantro leaves with tender stems

Instructions

1. Preheat oven to 325°F. Blend basil and oil in a food processor until smooth. Place lamb in a roasting pan. Season generously with salt and pepper and rub basil purée all over. Cover with foil, and cook until fork-tender, 3-3 1/2 hours. Increase oven temperature to 500°F. Remove foil and roast lamb until golden brown, 10-15 minutes. Let rest 30 minutes. Pour pan juices into a measuring cup and skim; set jus aside.
2. For polenta: Reduce oven temperature to 325°F. Mix thyme, shallot, garlic, polenta, cream, and 3 cups broth in a 13x9x2" baking dish; season with salt and pepper. Cover with foil and bake, without stirring, until polenta is softened and liquid is almost completely absorbed, 60-75 minutes. Thin polenta with more broth, if needed.
3. Reduce oven temperature to 325°F. Mix thyme, shallot, garlic, polenta, cream, and 3 cups broth in a 13x9x2" baking dish; season with salt and pepper. Cover with foil and bake, without stirring, until polenta is softened and liquid is almost completely absorbed, 60-75 minutes. Thin polenta with more broth, if needed.
4. For beans and assembly: Bring sugar, vinegar, chili paste, 1 teaspoon salt, and 1/3 cup water to a boil in a small saucepan. Add half of leeks, reduce heat, and simmer until soft, 8-10 minutes. Drain; set leeks aside. Wipe out saucepan. Cook bacon over medium heat until fat renders and bacon is crisp, about 5 minutes; transfer to a paper towel-lined plate. Add remaining uncooked leeks to saucepan and cook, stirring often, until soft, 8-10 minutes. Add beans, bacon, and reserved boiled leeks and cook until heated through, about 3 minutes; season with salt and pepper. Untie lamb and thinly slice. Divide polenta among bowls. Top with lamb, beans, and herbs; drizzle with jus.
5. Bring sugar, vinegar, chili paste, 1 teaspoon salt, and 1/3 cup water to a boil in a small saucepan. Add half of leeks, reduce heat, and simmer until soft, 8-10 minutes. Drain; set leeks aside.
6. Wipe out saucepan. Cook bacon over medium heat until fat renders and bacon is crisp, about 5 minutes; transfer to a paper towel-lined plate. Add remaining uncooked leeks to saucepan and cook, stirring often, until soft, 8-10 minutes. Add beans, bacon, and reserved boiled leeks and cook until heated through, about 3 minutes; season with salt and pepper.
7. Untie lamb and thinly slice. Divide polenta among bowls. Top with lamb, beans, and herbs; drizzle with jus.