2) Add the turkey to the brine, seal the bags and place in a shallow pan in the refrigerator for 5 to 7 days – just in case of leaking, check occasionally. Remove the breast from the brine, rinse and dry well.
3) For the rub, pulse all the spice ingredients in a spice grinder or food processor to a coarse paste. Rub the mixture all over the turkey breast. Wrap tightly in cling film and refrigerate resting in a bowl for 24 hours.
4) Soak the hickory chips submerged in water for 15 minutes. Place an oven rack 10cm below the grill and preheat the grill on high. Drain the chips and place in a 900g aluminium loaf pan. Grill the chips for 5 minutes, stir grill another 2 minutes. Remove to lower third of oven.
5) Preheat the oven to 130C/Gas 1/2. Place the turkey, skin side up, in a tin fitted with a roasting rack. Place the oven rack used to grill the chips into the centre of the oven and roast the turkey above the smoking chips for one hour.
6) Increase the heat to 180C/Gas 4. Carefully turn the turkey over and continue to roast until the internal temperature reaches 70C, another 1 hour 20 minutes. Remove the turkey from the oven. Cover loosely with foil and cool.
To make the sandwich:
1) Slice the pastrami very thin. Toast all the slices of bread.
2) Spread mayonnaise on 1 piece, layer pastrami, onions, tomato and lettuce on top. Spread mustard on the other piece of toast and place on top
3) Cut the sandwich in half diagonally. Repeat with remaining ingredients. Serve immediately.