Combine wine, vinegar and shallot in a small saucepan and bring to a boil. Reduce heat to medium-low and simmer until mixture is reduced to two tablespoons, 15-20 minutes.
To finish the sauce, whisk the three tablespoons of cold soy margarine a few pieces at a time into the warm reduction until you have a creamy sauce.
Stir in tarragon to taste and season with salt and pepper.