Preheat oven to 450 degrees F. Cover a large baking sheet with foil. Place a baking rack over the baking sheet and spray with nonstick cooking spray. (If no baking rack, just spray the foil).

Place the walnuts in a food processor and pulse until crushed into very small chunks. They should be small enough that they will easily stick to the chicken, similar in size to baking sprinkles. Set aside.

Cut chicken into 1-inch cubes, as even in size as possible to ensure even cooking.

Set up dredging station using shallow dishes, like pie plates, side by side: Combine flour, seasoned salt, garlic powder, kosher salt and pepper in one dish; the egg whisked with melted butter in the second dish; and spread the walnuts into the third dish.

Dredge one chicken cube through the flour, then the egg and finally the walnuts, pressing lightly to adhere to the chicken. Carefully arrange each piece on the prepared baking rack, placing smaller pieces towards the center. Repeat until all chicken pieces are coated. 

Bake in the preheated oven until the exterior is golden and crispy and the chicken is fully cooked; about 8-10 minutes.

Cook slightly on the baking rack before transferring to a platter to serve. Garnish with fresh parsley if desired.

To make the honey mustard dipping sauce, combine the ingredients until well mixed. Serve in a small bowl for dipping.