1. Prepare the filling: In a food processor, combine garlic, herbs, anchovy paste, lemon zest, and mustard. Pulse until finely chopped. With processor running, slowly add olive oil until a spreadable paste forms. Season with salt and pepper.
2. Prepare the lamb: If not already butterflied, lay lamb flat and make horizontal cuts to create an even thickness throughout. Season both sides with salt and pepper.
3. Stuff the lamb: Spread herb mixture evenly over the inside of the butterflied lamb, leaving a 1-inch border. Roll tightly from one long side, like a jelly roll.
4. Tie the roast: Using kitchen twine, tie the rolled lamb at 1-inch intervals to secure. Season the outside with salt and pepper, then rub with olive oil.
5. Prepare for roasting: Preheat oven to 450°F. Place onions, carrots, and garlic in a roasting pan. Set a rack over vegetables and place lamb on top.
6. Roast: Roast at 450°F for 15 minutes to develop crust. Reduce heat to 350°F and continue roasting until internal temperature reaches 130-135°F for medium-rare (about 1.5-2 hours total).
7. Baste: Every 30 minutes, baste lamb with pan juices. Add stock and wine to pan if it becomes dry.
8. Rest: Remove lamb from oven and tent with foil. Let rest 20-30 minutes before slicing.
9. Make gravy: Strain pan juices and vegetables, pressing to extract liquid. Skim fat and simmer to desired consistency.
10. Serve: Remove twine and slice lamb into 1/2-inch rounds. Serve with pan gravy.

Notes:

• Ask your butcher to butterfly the lamb for easier preparation
• The herb filling can be made 2 days ahead
• For best results, bring lamb to room temperature before roasting
• Save any leftover herb filling to mix with butter for bread

Storage Tips:

Store leftover lamb in an airtight container in the refrigerator for up to 5 days. The uncooked stuffed lamb can be prepared up to 24 hours in advance and refrigerated until ready to roast.