You will need at least a 6-quart Dutch oven for this recipe. Plan ahead: The chicken marinates for at least an hour before breading. Pressing the chicken after dredging it in the starch ensures a more uniform coating.
FOR THE CHICKEN: Process ginger and garlic in food processor until finely chopped, about 15 seconds; transfer to large bowl. Add water, soy sauce, sugar, and sesame oil and whisk to combine. Add chicken and press to submerge. Cover bowl with plastic wrap and refrigerate for at least 1 hour or up to 3 hours.
FOR THE DIPPING SAUCE: Whisk vinegar, soy sauce, and lemon juice together in bowl. Season with pepper to taste.
Line rimmed baking sheet with parchment paper. Set wire rack in second rimmed baking sheet. Whisk potato starch, sesame seeds, baking powder, 1 teaspoon salt, and 1 teaspoon pepper together in large bowl.
Working with 1 piece of chicken at a time, remove from marinade, allowing excess to drip back into bowl. Dredge chicken in potato starch mixture, pressing to adhere. Gently shake off excess and transfer chicken to parchment-lined sheet. Coating will look mottled; using your hand, press on chicken to smooth out coating. Cover sheet tightly with plastic and refrigerate for at least 30 minutes or up to 1 hour.
Add peanut oil to large Dutch oven until it measures about 2 inches deep; heat oil over medium-high heat to 375 degrees. Carefully add one-third of chicken to pot and fry until deep golden brown and cooked through, about 5 minutes, stirring gently as needed to prevent pieces from sticking together. Adjust burner, if necessary, to maintain oil temperature between 350 and 375 degrees.
Transfer chicken to prepared rack. Return oil to 375 degrees and repeat in 2 more batches with remaining chicken. Serve chicken with sauce.
1 (3-ounce) piece ginger, unpeeled, cut into 1/2-inch pieces
4 garlic cloves, peeled
1 cup water
½ cup soy sauce
3 tablespoons packed light brown sugar
1 tablespoon toasted sesame oil
2 pounds boneless, skinless chicken thighs, trimmed and halved crosswise
2 ¼ cups potato starch
2 tablespoons sesame seeds
1 ½ teaspoons baking powder
Salt and pepper
3 quarts peanut or vegetable oil
½ cup seasoned rice vinegar
¼ cup soy sauce
¼ cup lemon juice (2 lemons)