Chicken braised with wine, tarragon, and leeks is tender, aromatic, and delicious.
Season chicken with salt and pepper. Heat oil and butter in a large skillet over medium heat. Add chicken, skin side down; cook until skin is browned, about 5 minutes. Turn, and cook until other side is browned, about 3 minutes. Transfer to a plate; set aside.
Add leeks to skillet; cook until soft, about 3 minutes. Add tarragon; cook 1 minute. Add wine; deglaze pan, scraping up any browned bits from bottom, until liquid evaporates. Add stock and zest. Cover; bring to a boil. Return chicken to skillet; simmer, covered, over medium-low heat until cooked through, 35 to 40 minutes.
Transfer chicken to a platter; keep warm. Place skillet over high heat; cook until sauce thickens, 5 to 6 minutes. Stir in lemon juice. To serve, spoon sauce over chicken; garnish with tarragon sprigs.