Soak turkey for 15 mins in large container of water along with ½ cup vinegar and juice of 1 lemon. Wash turkey inside out with lemon, removing any slime, excess fat, feathers or other undesirables. Rinse and drain.
In a blender or food processor, puree all ingredients for the turkey seasoning (except butter).
Place turkey in a baking bag and pour marinade over turkey. Close bag and move around to completely cover with the seasoning. Marinate in the bag overnight or up to week in the refrigerator, turning once or twice.
When ready to cook, remove the turkey from fridge and bring to room temperature. Pre-heat oven to 350 degrees, min 30 minutes.
Now you have several options 1. Bake in the bag –seal tightly and bake for the required time according to instructions from manufacturer. 2. Remove from the baking bag and place on a roasting rack or baking pan. Remove the excess seasoning from the skin and brush with oil. Alternatively, you can layer the bottom of the roasting pan with 4 carrots, 2 onions, 4 celery, 2 sprigs parsley, bunch thyme, 6 cloves garlic and a hot pepper. Mix 4 cups chicken stock with 1 cup of the seasoning from the marinating bag and pour over the veggies. Then place the baking rack on top of the veggies and move the turkey from the bag onto the rack on the roasting pan.
Place turkey in the oven and cook for the required time based on weight and desired doneness level.
Once the turkey is done cooking, remove from the oven and tent with foil or parchment paper 15-20 mins to allow the juices to redistribute.
To make the stock, in a saucepan, add 4 cups of strained gravy and 2-3 tbs of flour and cook, whisking until sauce thickens slightly. Add salt, pepper and butter as required.