From Elizabeth Andoh's classic book, "At Home With Japanese Cooking". Chicken is marinated, dredged, and fried twice for extra crispiness. Serve it hot or cold. I recommend using thighs for this.
Cut the chicken into pieces about one inch square. In a shallow bowl, combine the soy sauce and sake, then stir in the grated fresh ginger. Lay the clove of garlic on your cutting board and whack it with the flat side of a broad-bladed knife or cleaver to loosen the skin. Remove the skin and place the smashed clove in the bottom of the bowl of marinade. Add the chicken pieces and let them marinate 20 minutes at room temperature or up to 8 hours covered and refrigerated.
Combine the flour, cornstarch, salt, and pepper in another shallow bowl or pan. Lift the pieces of chicken, one at a time, from the marinade and dredge them in the flour mixture. Shake off any excess flour and remove the coated chicken to a plate, letting it stand for 5 minutes. During this time the coating will absorb some of the marinade and the pieces will change from white to a beige color.
Heat the oil to 350 degrees (a pinch of the dredging mixture will sizzle inmmediately on the surface of the oil without burning) and fry the chicken pieces in batches of 4-5 each, for less than a minute. This first frying will seal the outer surfaces with a light-colored crust. Drain the chicken well on paper towels and lower the temperature of the oil to about 325 degrees (a pinch of the dredging mixture will sink slightly before sizzling). Re-fry the chicken, this time in batches of 6-7 pieces each, for 3-4 minutes. Drain the chicken again on paper towels, and serve it hot or at room temperature with lemon wedges.