Light a grill. Rub the lamb with oil, sprinkle with 1 teaspoon of the cumin and season with salt and black pepper. Let stand at room temperature for 10 minutes.

Meanwhile, in a bowl, combine the vinegar, honey, mustard and the remaining 1 teaspoon of cumin. Whisk in the 1/4 cup of oil and season with salt and white pepper.

Grill the lamb over moderate heat, turning a few times, until charred and medium-rare, about 12 minutes. Transfer the lamb to a carving board; let rest for 5 minutes.

In a large bowl, toss the romaine with the jicama, carrot, cucumber, shredded basil and jalapeños. Add the dressing and toss well. Transfer to plates. Thinly slice the lamb and arrange the slices on the salad. Garnish with the cilantro and basil sprigs and serve.