Preheat oven to 450°F. Lightly salt and pepper inside of turkey and smear inside with about 1/3 of the butter. Truss the turkey, dry the outside well, and rub skin all over with the remaining butter. Combine the oil and melted butter, set aside.
Set the turkey on a roasting rack, breast side up in the roasting pan, place in the oven for 15 minutes. Baste quickly with the oil and butter mixture. Reduce oven temperature to 325°F, distribute the onion, carrot and celery under the turkey, and baste again. Salt the turkey, continue roasting and basting every 30 minutes until done.
NOTE: TO TELL WHETHER THE TURKEY IS DONE, prick the thickest part of the drumstick with a fork; if the juices run clear or yellow, it is done. If not, roast another 5 minutes and test again. As a final check, lift the turkey and drain the juices from the cavity into the pan; if the last drops are clear or yellow, it is definitely done.
Transfer the turkey to a warmed platter; remove the string. Let stand, loosely tented in foil, at least 15 minutes before carving so juices will retreat into tissues.
Pour the juices and vegetables from the roasting pan into a strainer, pressing down to extract all the juices. Degrease the juices if you wish. Return ½ cup of fat to the roasting pan. Stir in the minced shallots and cook 2-3 minutes. Add flour, cook and stir 2-3 minutes, until smooth and bubbly. Add the degreased juices, the stock, and the Kitchen Bouquet. Boil rapidly over high heat, deglazing the pan. Cook 10-15 minutes, to develop flavor.
Carve the turkey (unless you are planning to carve at the table).