Lamb Vindaloo

Dry the lamb thoroughly with paper towels, then season generously with salt and pepper. Heat 2 teaspoons of the oil in a 12-inch skillet over medium-high heat until just smoking. Add half of the lamb to the skillet and cook, without stirring, until well browned on one side, about 4 minutes. Stir the meat and continue to cook, stirring occasionally, until completely browned, 4 to 6 minutes longer. Transfer it to the slow cooker. Return the skillet to medium-high heat and heat 2 more teaspoons oil until just smoking. Brown the remaining lamb and transfer it to the slow cooker.

Return the skillet to medium heat and heat the remaining 2 teaspoons oil until shimmering. Add the onions and ¼ teaspoon salt; cook, scraping the browned bits off the pan bottom, until the onions are softened and lightly browned, about 10 minutes. Add the garlic, paprika, cumin, cardamom, and cayenne; cook until fragrant, about 30 seconds. Add 2 cups of the chicken broth, the tomatoes, bay leaves, vinegar, and sugar, scraping the browned bits off the pan bottom; turn the heat to high and bring to a boil. Transfer to the slow cooker.

Cover and cook, on either low or high, until the lamb is tender, 6 to 7 hours on low or 4 to 5 hours on high.

Discard the bay leaves. Set the slow cooker to high (if necessary). Whisk the flour with the remaining ½ cup chicken broth until smooth, then stir into the slow cooker. Continue to cook on high until the sauce is thickened and no longer tastes of flour, 10 to 15 minutes longer. Before serving, stir in the cilantro and season with salt and pepper to taste.