Step 1: Marinate the Chicken

1. Prepare the chicken: Cut boneless, skinless chicken thighs into bite-sized pieces (~1 ½ inches).
2. Mix the marinade: In a large bowl, combine soy sauce, oyster sauce, sugar, garlic, ginger, sesame oil, eggs, salt, and black pepper. Whisk well to blend the flavors.
3. Coat the chicken: Add mochiko flour and cornstarch to the marinade. Mix until the chicken pieces are fully coated in the thick batter.
4. Marinate: Cover and refrigerate for at least 4 hours (ideally overnight) to allow the flavors to absorb.

Step 2: Heat the Oil

1. Use a deep frying pan or Dutch oven and heat 1 inch of vegetable oil to 350°F (175°C).
2. Test the oil: Drop a small bit of batter into the oil—if it sizzles immediately and floats, the oil is ready.

Step 3: Fry the Chicken

1. Shake off excess batter: Take each chicken piece out of the marinade and let excess batter drip off.
2. Fry in batches: Add the chicken to the hot oil, frying 4–5 pieces at a time. Cook for 3–4 minutes per side until golden brown and crispy.
3. Drain excess oil: Remove chicken and place it on a wire rack or paper towels to keep it crispy.

Step 4: Serve and Enjoy!

1. Garnish with sliced green onions, sesame seeds, and lemon wedges.
2. Serve immediately with steamed rice, macaroni salad, or dipping sauces like spicy mayo or tonkatsu sauce.