Preheat a grill or grill pan on medium heat.
In a bowl, whisk together the ingredients for the marinade. Season with salt and pepper to taste.
Cook the chicken: Brush one side of the chicken with the marinade and season with salt and pepper. Then place that side down on the grill or grill pan. Brush the top side with marinade and season with salt and pepper. Cook on one side until nicely marked for about 6 minutes then flip over and brush with marinade again. Cook to an internal temperature of 160 degrees for about 6 minutes more. While the chicken is cooking, toast the bread.
Toast bread on the grill.
Prepare the carrots per the instructions above.
Once the chicken is cooked, set aside to rest for 2 to 3 minutes.
Make the sandwich: Spread mayo on the inside of both halves of the toasted bread. Layer with lettuce, tomato, chicken, cheese, and onion.
Serve: enjoy the sandwich with carrot sticks, ranch, and kombucha.