Grilled Lamb Salad
Lamb: Place peppercorns, fennel, and salt in spice grinder and grind coarsely. Add garlic and process until garlic is finely chopped. Transfer to a bowl and stir in the olive oil. Spread over the lamb and marinate overnight (or at least four hours). Grill or broil for 10-15 minutes on each side, let rest 10 minutes.
Vinaigrette: Whisk together the rhubarb, mustard, salt, sugar, and vinegar. Slowly beat in the oil to emulsify. Cover and refrigerate.
Salad: Toss the greens with the dressing and place on individual plates or a large platter. Thinly slice the lamb and arrange over the salad. Serve immediately.