Marinate the Chicken: In a bowl, combine the chicken pieces with grated garlic, ginger, light soy sauce, sake, sesame oil, white pepper, and salt. Cover and refrigerate for at least 30 minutes to allow the flavors to meld.
Coat the Chicken: Place potato starch in a shallow dish. Dredge each marinated chicken piece in the potato starch, ensuring the coating adheres well. Shake off any excess starch.
Fry the Chicken: Heat oil in a Dutch oven or deep frying pan to 350°F. Fry the chicken in batches for about 4 minutes, ensuring the oil temperature stays consistent (above 300°F). Use a mesh strainer to remove any loose pieces of coating.
Double Fry for Crispiness: Once all batches are fried, return the oil to 350°F. Fry the chicken a second time for 1-2 minutes or until the coating is deep golden brown and crispy.
Prepare the Spicy Mayo Dipping Sauce: In a bowl, mix Japanese mayo, sriracha, grated garlic, lemon juice, salt, and pepper.
Serve and Enjoy: Optional: Squeeze fresh lemon juice over the chicken before serving. Dip the crispy Chicken Karaage pieces into the spicy mayo sauce and enjoy!