In a large mixing bowl, whisk together mochiko flour, potato starch, eggs, sugar, gluten-free soy sauce, mirin, chopped scallions, minced garlic, and grated ginger until smooth.

Cut the chicken thighs into 2-inch strips and coat them with the prepared marinade. Refrigerate for at least 4 hours or preferably overnight.

Heat enough vegetable oil in a Dutch oven to reach 3 inches deep to 350°F (175°C).

Carefully fry the marinated chicken pieces in batches for about 4-5 minutes until golden brown and crispy. Drain on a wire rack.

Drizzle the cooked chicken with spicy mayo and sprinkle with furikake before serving warm.