Put the vinegar, wine and shallots into a small saucepan and simmer to reduce the liquid to 1-2 tbsps. Strain this reduction and return to the pan with the wasabi and soy . Then, over a very gentle heat, whisk in the cubes of butter, one at a time, so that the sauce emulsifies. Be very careful it does not boil as it will split. Once most of the butter is in you can add a couple of cubes at a time.