Ingredients

• 1 1/2 pounds small new or Yukon Gold potatoes, scrubbed
• Kosher salt
• 2 racks of lamb (about 2 pounds total)
• Freshly ground black pepper
• 4 tablespoons olive oil, divided
• 2 garlic cloves, chopped
• 1/2 cup chopped fresh flat-leaf parsley
• 1/4 cup chopped fresh dill
• 1 tablespoon Dijon mustard
• 2 teaspoons cumin seeds, crushed
• 6 cups watercress leaves with tender stems
• 2 teaspoons Sherry vinegar

Instructions

1. Place potatoes in a large saucepan and cover with 1" cold water; season with salt. Bring to a boil, reduce heat, and simmer until tender, 10–15 minutes. Drain.
2. Meanwhile, preheat oven to 400°F. Season lamb with salt and pepper. Heat 2 tablespoons oil in a large skillet over medium-high heat. Cook lamb, turning occasionally, until golden brown all over, 6–8 minutes; transfer to a foil-lined baking sheet, placing fat side up.
3. Mix garlic, parsley, dill, mustard, cumin, and 1 tablespoon oil in a small bowl; season with salt and pepper.
4. Spread herb mixture over lamb and roast until an instant-read thermometer inserted into thickest part of meat registers 130°F for medium-rare, 18–22 minutes. Transfer to a cutting board and let lamb rest 5 minutes before cutting into double chops.
5. While lamb is resting, heat remaining 1 tablespoon oil in a medium skillet over medium heat. Add potatoes and watercress and cook, tossing, until watercress is just wilted, about 1 minute. Mix in vinegar and season with salt and pepper. Serve lamb with watercress and potatoes.