Roast Leg of Lamb, Cauliflower & Shallots

Preheat oven to 425 degrees F.

Place tarragon and parsley in a food processor. Add 2 tablespoons oil, mustard, garlic, lemon zest, 1 teaspoon salt and pepper and process until fairly smooth. Transfer 3 tablespoons of the mixture to a medium bowl; set aside for Step 6.

If your lamb is in the oven-safe netted bag used by most supermarkets, remove the bag. Open the lamb so it's flat. Spread three-fourths of the remaining herb mixture over the surface of the lamb. Roll the lamb closed and tie in several spots with kitchen string so it is about the shape of a large football; transfer to a large roasting pan and spread the remaining herb mixture over the top and sides.

(If you prepared the recipe to this point the day before, let the lamb stand at room temperature while you prepare the vegetables.) Leaving the root end intact, peel and halve shallots (quartering larger ones). Trim and cut cauliflower (or romanesco) into 2-inch florets. Combine the shallots and cauliflower in a large bowl with the remaining 2 tablespoons oil and 1 teaspoon salt.

Roast the lamb in the center of the oven for 20 minutes. Add the vegetable mixture to the pan around the lamb. Continue to roast, stirring the vegetables every 20 minutes or so, until they are golden brown and an instant-read thermometer inserted into the thickest part of the meat registers 140 degrees F (for medium-rare) to 145 degrees (for medium), 1 hour to 1 hour 20 minutes more. Transfer the lamb to a clean cutting board and let rest for 10 minutes. Stir capers into the vegetables.

Add lemon juice and sour cream to the bowl with the reserved herb mixture; stir to combine. Slice the lamb and serve with the vegetables and sauce.