01 - Preheat the oven to 375°F. Pat the turkey breast dry with paper towels to ensure crispy skin.
02 - In a small bowl, mix softened butter, olive oil, chopped rosemary, thyme, sage, garlic, lemon zest, salt, and pepper to form a consistent herb paste.
03 - Gently loosen the skin of the turkey breast and rub half the herb paste under the skin. Rub the remaining paste evenly over the outside.
04 - Arrange onion, carrots, and celery in a roasting pan. Pour 1 cup chicken broth into the pan. Place the turkey breast skin-side up on top of the vegetables.
05 - Roast uncovered for 1½ hours, or until the internal temperature reaches 165°F in the thickest part. Baste with pan juices every 30 minutes for moisture.
06 - Transfer the turkey breast to a platter, tent with foil, and rest for 15 minutes before slicing to retain juices.
07 - For the gravy, strain pan drippings and discard vegetables. In a saucepan, melt butter over medium heat. Whisk in cornstarch to form a roux.
08 - Gradually whisk in 2 cups broth and 2 tbsp pan drippings. Simmer, whisking constantly, until thickened (about 5–7 minutes). Season with salt and pepper.
09 - Slice turkey and serve with warm herb gravy.