In a medium bowl, combine the chicken pieces, soy sauce, garlic, and ginger. Toss until the chicken is fully coated in the marinade. Cover and refrigerate for at least 30 minutes or up to 8 hours for deeper flavor.
Pour enough oil into a large Dutch oven or wok to reach about 2 inches in depth. Heat over high heat until the oil reaches 350°F.
While the oil heats, whisk together the cornstarch and all-purpose flour in a medium bowl.
Remove the chicken from the marinade, letting any excess marinade drip off. Toss the chicken pieces in the flour mixture until they’re fully coated, then transfer them to a strainer basket. Shake the basket gently to remove any excess flour.
Carefully lower the chicken pieces into the hot oil. You’ll notice the temperature drop slightly to about 300°F. Adjust the heat to maintain this temperature for consistent frying.
Fry the chicken for 5 to 7 minutes, stirring occasionally with chopsticks or a wire mesh spider, until the pieces are deeply golden and cooked through.
Transfer the cooked chicken to a plate lined with paper towels to drain. While still hot, sprinkle lightly with kosher salt for extra flavor.
Serve immediately, garnished with scallion slices and paired with lemon wedges for a bright, zesty finish.