Cook potatoes in a large pan of boiling water for 12-15 minutes until just tender. Add beans for final minute, then drain. Rinse under cold water, then drain again. Quarter potatoes lengthways.
Meanwhile, heat a lightly oiled chargrill pan or large frypan on high heat. Cook lamb for 3 minutes each side for pink, or until cooked to your liking. Remove from heat and rest lamb in pan for 5 minutes.
Meanwhile, mix all the dressing ingredients in a large bowl and season to taste with salt and pepper. Add the potato, beans, watercress and witlof and toss to combine. Divide the salad among plates, then slice the rested lamb and serve on the salad.
Serving size: 4
Recipe courtesy of taste.com.au