Caramelize the sugar light brown. Deglaze with soy sauce and chicken stock. Boil up once until the sugar has dissolved. Stir starch and 4 tbsp.
cold water until smooth. Stir into the boiling Teriyaki sauce and bring to the boil once. Let it cool down. Pour into clean screw-top glasses or bottles, close and chill (lasts 4-6 weeks)