Add the soy sauce, Worcestershire sauce, oyster sauce, rice vinegar, tomato sauce (or ketchup), raw sugar, hoisin sauce, ginger and Japanese 7 Spice powder into a small bowl and mix well.
Taste, and add a little of any ingredient until you're satisfied with the flavour.
Store in an airtight container in the fridge until you’re ready to use. Aim to use within a couple of days for the best flavour.
