Brine the turkey
Combine the maple syrup, sugar, soy sauce, salt, garlic, bay leaves, and peppercorns in a 5- to 6-quart pot. Add 3 quarts water and simmer until the sugar and salt dissolve. Cool completely. Place the turkey breast in the pot, skin side down (it’s ok if some of the backbone sticks out). Refrigerate, loosely covered, for at least 4 hours and up to 18 hours.
Make the gravy
Heat 2 Tbs. of the butter and the oil in a 12-inch skillet over medium heat. Add the shallot and cook, stirring, until soft but not brown, 1 to 2 minutes. Add the mushrooms, season lightly with salt, and cook, stirring infrequently, until any liquid they release has evaporated and they are well browned, 5 to 6 minutes. Add the stock and sherry, and cook over high heat until reduced to about 2-1/2 cups, about 15 minutes; it will be thickened later. (The gravy can be prepared to this point up to 2 days ahead. Refrigerate and reheat gently before proceeding.)
Roast the turkey and finish the gravy
Position an oven rack in the lower third of the oven, and heat the oven to 350°F. Remove the turkey breast from the brine, rinse it well, and pat dry with paper towels. Discard the brine. Place the breast skin side up on a rack in a roasting pan. Roast until the skin is golden brown and an instant-read thermometer registers 160°F in the thickest area of the breast, about 2 hours (begin checking earlier if your bird is on the smaller side). If the skin is overbrowning, cover the breast loosely with aluminum foil.
Transfer to a carving board, tent with foil, and let rest for 15 to 20 minutes.
Just before serving, bring the gravy to a simmer over medium-low heat. Mix the cornstarch with 3 Tbs. water. Stir this mixture into the gravy, a little at a time, until thickened to your liking (you may not need it all). Whisk in the remaining 2 Tbs. butter, the chives, parsley, and tarragon, and season to taste with salt and pepper.
Carve the turkey breast, and serve with the gravy.
nutrition information (per serving):
680, Fat Calories
30, Saturated Fat
10, Polyunsaturated Fat
6, Monounsaturated Fat
Photo: Scott Phillips