1 Debone chicken thighs and place on a work surface, skin side down. Score the flesh with a sharp knife. Press on the meat to spread it out, creating an even thickness.
2 Combine ginger, 2 tablespoons sake and soy sauce in a large bowl. Coat the chicken, and set aside to marinate for 20 minutes, turning occasionally.
3 Drain chicken and place skin side down on working surface. Cut spring onions to the same length as the chicken and place 3 or 4 pieces across each piece of chicken. Sprinkle with an even coating of cornstarch.
4 Roll each piece of chicken up and fasten with kitchen string, securing at both ends.
5 Heat oil in 25-cm (10-in) skillet over medium-high heat. Add chicken rolls, seam side down, and cook, turning chicken frequently with tongs, until evenly browned.
6 Drain fat from skillet, leaving chicken in place, and add sake. Reduce heat to medium-low, cover and cook for 7 minutes.
7 Add reserved marinade and cook chicken roll for 10 to 12 minutes, or until tender.
8 To serve, remove string from meat and slice crossways in 2-cm (¾-in) thick slices and spoon pan juices over the slices.