If you are baking these in an oven, preheat your oven to 375º F. See the Notes section for oven directions.
Cut the chicken breasts into chicken chunks and put into a mixing bowl.
Pour the ranch dressing over the chicken and mix to coat the chicken evenly.
Cover the bowl with plastic wrap and allow the chicken to marinate for at least 15 minutes. You can cover them and put them into the refrigerator overnight if you plan to meal prep these for the next day.
Preheat your air fryer to 400º F.
Add the bread crumbs and parmesan to a bowl and mix well.
Put 4-5 chicken chunks into the bread crumb mixture and toss to coat them evenly with bread crumbs.
Spray the air fryer basket with cooking oil (do not use olive oil!) and add coated chicken to the basket. Make sure to have space between each nugget so air can circulate around each one. This will help make your nuggets crispier.
Spray the top of the nuggets with oil and cook for 10 minutes.
Remove the basket when they are done and check the internal temperature of the largest nuggets to ensure they are 165º F.