Nutrition per serving may change if servings are adjusted.
2 12-ounce boneless lamb loins, trimmed
3 teaspoons extra-virgin olive oil, divided
Salt & coarsely ground pepper to taste
1/4 cup finely chopped shallots
1 cup lamb stock (see Note), or reduced-sodium chicken broth
3 tablespoons balsamic vinegar
2 teaspoons Worcestershire sauce
1 teaspoon reduced-sodium soy sauce
1 bunch watercress, trimmed, washed and dried (4 cups)
Preheat oven to 450 °F. Heat a heavy ovenproof skillet over high heat. Brush the lamb loins with 1 teaspoon of the oil and sprinkle with salt and pepper. Sear the lamb on all sides, about 2 minutes per side. Transfer the pan to the oven and roast until the lamb is medium-rare (120 to 130 °F on an instant-read thermometer), about 8 minutes. Remove the lamb from the pan and set it aside on a carving board tented with foil to keep warm.
Without washing the pan, place it over medium heat. Add shallots and the remaining 2 teaspoons oil. Cook the shallots, stirring, until softened, about 1 minute. Add stock or broth, vinegar, Worcestershire sauce and soy sauce; stir, scraping up any browned bits. Increase the heat to high and boil the sauce until it has reduced to 1/2 cup, about 5 minutes. Season with salt and pepper.
Thinly slice the lamb. Toss watercress in 2 tablespoons of the warm sauce until slightly wilted and arrange on 6 warmed dinner plates. Fan the lamb slices alongside. Drizzle the remaining sauce over the lamb and serve.
Note: For this recipe, order a saddle of lamb and ask the butcher to bone it, saving the bones for stock. To make lamb stock, brown the bones and some chopped onions, carrots and celery in a hot oven. Transfer the roasted bones and vegetables to a stock pot, add a bouquet garni (sprigs of parsley and thyme tied together with string), peppercorns and water to cover. Simmer for 3 to 4 hours, strain and refrigerate.