Bring one cup of water to a boil in a medium sized saucepan. Then add in the salt and sugar and whisk until completely dissolved. Remove from heat and add in six heaping cups of ice and whisk till ice melts and water is cold.
Place the chicken on a piece of plastic wrap, then fold the plastic over the chicken leaving plenty of space between the edge of the chicken and the plastic.
Using a rolling pin, or meat tenderizer, pound the thick portion of the chicken until it's as close to the thickness of the thin side as possible. I aim for about 3/4" thick all around.
Place the chicken in a bowl and add the cold brine, ensuring the chicken it's completely submerged. Then, place the bowl in the refrigerator for at least 30 minutes, 4-6 hours is even better.
Light your grill and set up for medium high direct heat. While the grill is preheating, remove the chicken from the brine and pat dry with a paper towel. Then, evenly coat the chicken with mayonnaise and lightly season with your favorite chicken seasoning.
Place the chicken on the grill, directly over medium high heat. Grill for two minutes per side before flipping. Do this for a total of about 6-8 minutes depending on the thickness of the chicken, until the internal temperature reaches 150 - 153 °F.
Remove the chicken from the grill, tent with aluminum foil and let rest for 3-5 minutes. Serve hot with rice or grilled baby bok choy.