Combine pesto, garlic (If using) and vinegar in a food processor. Pulse just until combined.
With the food processor running, slowly drizzle in olive oil and continue processing until emulsified. Season to taste with salt and pepper.
Store in the refrigerator. Will keep for a few days.
You can substitute red wine vinegar for the white wine vinegar in a 1 to 1 ratio. Balsamic will alter the color. Avoid distilled or apple cider vinegar as the flavors would be too harsh. Store in the refrigerator but because the olive oil will solidify in the cool temperatures, I recommend allowing the dressing to come to room temperature before serving. Giving it a little whisk will help too. Nutrition information for estimation purposes only.