Step 1

Whisk together soy sauce, sake, sesame oil, ginger, garlic, salt, and pepper in a large bowl until combined. If using bone-in chicken thighs, carefully remove bones using a sharp knife to cut around bones; discard bones or reserve for stock. Cut chicken thighs into 2-inch pieces. Gently stir chicken into soy sauce mixture until fully coated; cover and refrigerate 30 minutes.

Step 2

Pour oil to a depth of 1 1/2 inches (about 6 cups) in a medium Dutch oven and heat over medium until a deep-fry thermometer registers 325°F.

Step 3

While oil is heating, place flour in one shallow dish and place potato starch in a second shallow dish. Working with a few pieces at a time, remove chicken from marinade, shaking off excess marinade. Add chicken to flour, and toss gently to coat; shake off any excess flour. Add chicken to potato starch, and toss gently to coat; shake off any excess. Repeat process with remaining chicken pieces.

Step 4

Line a large rimmed baking sheet with paper towels; place a wire rack over paper towels. Working in about 4 batches, add dredged chicken pieces to hot oil. Cook, gently stirring often, until light golden brown, about 90 seconds. Using a slotted spoon, transfer chicken to prepared baking sheet to drain. Repeat with remaining chicken pieces, returning oil temperature at 325°F between batches.

Step 5

Increase heat to medium-high, and heat oil until deep-fry thermometer registers 350°F. Adjust heat as needed to maintain temperature. Working in batches, add fried chicken pieces to hot oil, and fry, gently stirring often, until golden brown and crispy and a meat thermometer inserted in thickest part of chicken piece registers 165°F, about 45 seconds. Remove chicken from oil using a spider or slotted spoon; transfer to prepared baking sheet. Continue process with remaining chicken pieces, letting oil temperature return to 350°F between batches. Serve hot, and garnish with lemon wedges and shichimi togarashi.