Line the air fryer basket with parchment paper. Preheat the air fryer to 400°F if your model recommends preheating.
In a medium bowl, whisk together the all-purpose flour and cornstarch.
In a separate bowl, whisk together the buttermilk and egg until combined.
Working a few pieces at a time, coat the chicken: first dredge each piece in the dry flour mixture, then dip into the buttermilk-egg mixture, then dredge again in the dry mixture. Place the breaded pieces in a single layer on a plate or tray while you finish breading the rest.
Place a single layer of breaded chicken pieces in the prepared air fryer basket. Cook in batches as needed so pieces do not overlap.
Air fry at 400°F for 8 minutes. Open the basket, carefully flip each piece, then return to the air fryer and cook an additional 5–8 minutes, or until the exterior is crisp and an instant-read thermometer inserted into the center of a piece reads 165°F.
While the chicken cooks (or immediately after removing it), make the sauce: in a small saucepan over medium heat combine Frank’s Red Hot Sauce, butter, and garlic powder. Whisk until the butter melts and the sauce is smooth, then remove from the heat and let the sauce cool to room temperature.
Transfer the cooked nuggets to a bowl, pour the cooled buffalo sauce over them, and gently toss to coat. Cooling the sauce before adding it helps keep the breading crisp.
Serve the sauced chicken immediately.