Place the chicken breasts into a food processor fitted with the steel blade. Pulse 4 or 5 times just to begin to break them down into smaller pieces. Add the egg, garlic powder, onion powder, paprika salt and pepper. Continue to pulse until the chicken resembles hamburger meat. (It’s ok if there are a few pea-sized pieces of chicken remaining.) Add ¼ cup of breadcrumbs and pulse until evenly and completely distributed throughout the mixture.
Line a baking sheet with parchment paper and spray it with cooking spray. Scoop golf ball-sized amounts of the chicken mixture and place them on the greased parchment paper. (Using the same-sized scoop that you use for cookies is perfect here.) Spray the tops of the ground chicken with a quick spritz of cooking spray and press with your fingers to flatten the tops and form the balls into nuggets. Place the nuggets into the freezer for approximately 1 hour to allow them to firm up enough to be breaded. While the nuggets are in the freezer, preheat the oven to 375 degrees and add the remaining breadcrumbs to a plate (approximately 1¾ cups).
When the nuggets are completely firm, remove them from the freezer and coat each nugget in breadcrumbs. (The nuggets should not be rock solid. They should be just firm enough to handle, but still “sticky” enough on the exterior, for the breadcrumbs to stick.) Bread each nugget by lightly pressing the breadcrumbs into the chicken to ensure that they adhere. Once breaded, place them back on the baking sheet while you coat the others.
Spray the tops of the breaded nuggets with another spritz of cooking spray and bake for 12–14 minutes. The nuggets will be firm in the centers when pressed. (Cooking times may vary depending on how thick your nuggets are and how long they’ve been out of the freezer. Cut one open to check for doneness if you are concerned they may be undercooked.)
Make a batch ahead of time to keep for an easy weeknight meal. Once the chicken is breaded, just store it in the freezer.