- 3/4 cup (1 1/2 sticks) unsalted butter, room temperature
- 3 tablespoons chopped fresh tarragon
- 3 tablespoons chopped fresh mint
- 4 teaspoons tarragon vinegar
- 2 teaspoons coarse kosher salt
- 1 6 1/2-pound leg of lamb with bone, well trimmed
- 1 tablespoon 1-inch-long very thin strips orange peel (orange part only)
- 2 tablespoons olive oil
- Coarse kosher salt
- 2 cups dry red wine
- 1 1/3 cups low-salt chicken broth
- 2 teaspoons finely grated orange peel
- Fresh tarragon and mint sprigs (for garnish)
- Stir butter, tarragon, mint, tarragon vinegar, and 2 teaspoons coarse salt in medium bowl until well blended. Transfer 1/4 cup herb butter to small bowl and reserve for vegetables. DO AHEAD: Can be made 1 day ahead. Cover both bowls and chill. Bring medium bowl of herb butter to room temperature before using.
- Using small sharp knife, make 1-inch-deep slits all over lamb. Insert 3 or 4 orange peel strips into each slit. DO AHEAD: Can be made 1 day ahead. Enclose lamb in plastic wrap and chill.
- Position rack in bottom third of oven and preheat to 450°F. Heat oil in very large skillet over medium-high heat. Sprinkle lamb with coarse salt and pepper. Add lamb to skillet; cook until brown on all sides, about 8 minutes. Transfer to roasting pan. Brush with 2 tablespoons herb butter. Roast lamb 15 minutes. Brush again with 2 tablespoons herb butter.
- Reduce temperature to 350°F. Continue to roast lamb until thermometer inserted into thickest part registers 135°F to 140°F for medium-rare, about 55 minutes. Transfer lamb to platter; reserve pan. Tent lamb loosely with foil; let rest 30 minutes.
- Spoon fat off any juices in roasting pan. Place pan over 2 burners on high heat. Add wine and broth and bring to boil, whisking to scrape up browned bits. Boil until sauce is reduced to 2 cups, about 5 minutes. Whisk in remaining herb butter and grated orange peel. Season sauce to taste with coarse salt and pepper.
- Spoon vegetables around lamb on platter; garnish with fresh herb sprigs. Serve with sauce.