Preheat your oven to 450°F or set the air fryer to 375°F if you choose that option.

Lay plastic wrap over your cutting board and place the chicken breast on top. Fold the wrap over the chicken and gently pound it to a thickness of about 3/4 inch. Remove the wrap and cut the chicken into 1-inch cubes.

Spread Panko breadcrumbs on a baking sheet and toast them in the oven or air fryer for 5 to 7 minutes until they become light golden brown.

In a bowl, combine the melted butter, garlic salt, black pepper, and parsley until thoroughly mixed. In another bowl, combine the toasted Panko crumbs with the Parmesan cheese.

Quickly coat the chicken cubes in the butter mixture, ensuring they are evenly covered. Then, dredge each piece in the Panko-Parmesan mixture until they're fully coated. Arrange them on a baking sheet leaving around 2 inches of space between each nugget.

Bake the nuggets on the middle rack of your preheated oven for 12 to 15 minutes. For extra crispiness, move them to the top rack for the last 3 minutes.

If using an air fryer, arrange the nuggets in a single layer (spray the basket lightly if desired). Cook for 10 minutes, shake the basket to turn the nuggets, and cook an additional 2 minutes until they're crispy.

Let the nuggets rest for 2 to 3 minutes before serving; this will help keep them juicy inside. Enjoy your homemade crispy chicken nuggets with your favorite dipping sauce.