Preheat oven to 375º and spray a baking sheet with cooking spray.
Place macadamia nuts and coconut in a food processor and process until finely ground. Add panko crumbs and give the mixture a quick whirl to mix the panko in. Pour onto a plate.
Place flour on a separate plate. Mix together egg and milk in a bowl.
Sprinkle chicken with salt and pepper. Coat lightly in flour, dip in egg mixture, and then roll in coconut mixture. Place on baking sheet and spray chicken with cooking spray. Bake for 15 minutes or until no longer pink in center.
In a small saucepan, combine pepper jelly, peaches, mustard, and horseradish. Bring to a simmer for 5 minutes. Let cool to room temperature.