In a small bowl, combine the mayo, sour cream, miso paste, garlic powder, and vinegar. Give it a good whisk or two to incorporate all the ingredients. Add salt and pepper to taste.
If the dressing is too thick, add a tablespoon of soy milk (unsweetened plain) and stir to combine.
Crumble the tofu into the mixture and stir to combine.
Store the dressing in a glass jar in the fridge for up to 7 days.