Slice the chicken lengthwise, then chop into bite-sized pieces.
Mix the soy sauce, sake, garlic and ginger then toss with the chicken pieces, making sure they're all well covered.
Leave to marinate for a minimum of 15 minutes, longer if you have time. Soak up the liquid with paper towel, then they won't sputter in the oil.
Put the chicken pieces in a plastic bag, add the corn-starch and shake the bag well until the chicken pieces are evenly (but not thickly) coated.
Heat plenty of oil in a wok or a deep pan and fry the chicken until light brown. Drain them on paper towels.
Serve with the lemon wedges, wasabi mayonnaise or another Japanese-style dip.