Step 1

In a small bowl, combine 2 tablespoons of the oil with the garlic, shallot and herbs. Lay the loins on a work surface, fat side down, and season with salt and pepper. Spread the herb paste all over the lamb. Roll each loin over the tenderloin and rib apron to make a neat roulade. With butcher's twine, tie the meat at 1-inch intervals. Season the lamb with salt and pepper.

Step 2

Preheat the oven to 350°. In a 12-inch skillet (preferably cast-iron), heat the remaining 1 tablespoon of olive oil until shimmering. Add the lamb loins and cook over moderate heat, turning, until browned all over, about 20 minutes total.

Step 3

Transfer the skillet to the oven and roast the loins for 10 minutes, until an instant-read thermometer inserted in the thickest part registers 125°. Transfer the loins to a carving board to rest for 10 minutes.

Step 4

Cut off the strings. Carve the loins into 1-inch-thick slices and serve.