After I mix the ingredients together, I like to store mine in a small Mason jar, so that I can shake it well before using (in case the oil & vinegar have separated). The addition of a small amount of mayonnaise helps keep the dressing stabilized. I usually use Champagne vinegar, but a good red wine vinegar or fresh squeezed lemon juice will work as well.
After I mix the ingredients together, I like to store mine in a small Mason jar, so that I can shake it well before using (in case the oil & vinegar have separated). The addition of a small amount of mayonnaise helps keep the dressing stabilized. I usually use Champagne vinegar, but a good red wine vinegar or fresh squeezed lemon juice will work as well.
Adding all the olive oil at once guarantees an oily puddle instead of an emulsion. Home cooks frequently dump liquids together and wonder why the dressing breaks instantly. Whisking the vinegar, finely minced shallot, Dijon, and a fractional half-teaspoon of mayonnaise first creates a continuous aqueous phase capable of holding fat droplets in suspension. Pouring the extra-virgin olive oil in a slow, controlled stream while constantly agitating the bowl forces mechanical dispersion, yielding a glossy, lightly thickened final product rather than a watery separation.
Emulsions rely on emulsifiers possessing both hydrophilic and lipophilic properties to bridge the gap between oil and vinegar. Mustard and egg proteins contained in mayonnaise act as these vital chemical bridges. Storing the finished dressing in a sealed glass jar at room temperature for up to two hours allows the flavors of fresh tarragon and parsley to meld properly without chilling the fats into solidity.