Brining: 

1. Fill a large container with 1 gallon of water.
2. To water, whisk and add in kosher salt, brown sugar, bay leaves, thyme, and black peppercorns.
3. Pat dry skin-on turkey breast. Submerged into the brine. Cover and fridge overnight.
4. Pat bird completely dry. Place on a wire rack set over a rimmed baking sheet lined with foil. Optionally coat with vegetable oil and additional seasoning.
5. Place into a 400℉ oven for 30 minutes or until an internal temperature of 163℉.
6. Let rest until room temperature. Wrap and fridge until completely cold (3 hours to overnight).
7. Thinly slice before serving.

Sandwich: 

1. In a medium bowl, add in mayonnaise, yellow mustard (or dijon), chopped parsley, 2 cloves of grated garlic, and season to taste with fresh ground black pepper and kosher salt. Mix together until combined.
2. In a large skillet, heat oil over medium-high heat until it simmering. Add in tomatoes and let sear/char for about 3 minutes. Remove once seared/charred, place to side and season with salt and fresh crack black pepper.
3. Thinly slice red onions. Place into a bowl covered with a wire rack and fill with water. Run water over onions for about 30 seconds. Drain.
4. Slice 8 slices of bread. Optionally toast the bread using a toaster or over melted butter in a pan.
5. On both halves of bread, spread on a generous amount of the mustard mayo sauce followed by lettuce, tomatoes, thinly sliced red onions, sliced turkey, and swiss cheese.
6. Top with the other half of bread, slice and enjoy.