Preheat the oven to 390°F (199°C), or preheat an air fryer to 390°F (199°C).
Trim any fat from the chicken breast and slice it into 1/2-inch thick slices, then cut each slice into 2–3 nugget-sized pieces.
Place the melted unsalted butter in a small bowl.
In a mixing bowl, whisk together the rice flour, garlic powder, paprika, salt, and black pepper until evenly combined.
Dip each chicken piece into the melted butter, then dredge it in the seasoned rice flour mixture, pressing gently so the coating adheres. Shake off excess.
Arrange the coated nuggets in a single layer on a parchment-lined baking sheet (or place them in a single layer in the air fryer basket).
If baking, bake for 15–18 minutes until golden brown and cooked through; if air-frying, air-fry for 7–8 minutes until golden and cooked through. Cook time may vary with nugget size—ensure internal temperature reaches 165°F (74°C).
Let the nuggets rest a minute before serving.
