Cut the chicken: Cut the chicken breasts into evenly sized, bite-sized nugget pieces.
Marinate: Combine buttermilk, salt, garlic powder, onion powder, paprika, and black pepper. Add the chicken and coat well. Cover and refrigerate for at least 30 minutes.
Prepare the breading: Mix flour, cornstarch, paprika, garlic powder, onion powder, salt, black pepper, and baking powder in a shallow bowl.
Coat the nuggets: Remove each chicken piece from the marinade, let the excess drip off, then coat thoroughly in the flour mixture.
Heat the oil: Heat frying oil in a heavy-bottomed pan to approximately 350°F (175°C).
Fry: Fry the nuggets in small batches for about 3–5 minutes, or until golden, crispy, and cooked through.
Check temperature: Make sure the center of the chicken reaches 165°F (74°C).
Drain and serve: Transfer the nuggets to a wire rack and serve hot with your favorite dipping sauce.