Buttermilk (Best Option)
1:1 (1 cup buttermilk per 1 cup whole milk)Buttermilk works well because it has a similar fat content and viscosity to whole milk but with added acidity, which helps stabilize emulsions and enhances flavor complexity in salad dressings. The acidity also helps balance oil and vinegar components.
For best results, use fresh buttermilk and whisk thoroughly to integrate it evenly. If the dressing is too tangy, balance with a small amount of sweetener or adjust vinegar accordingly.
Compared to whole milk, buttermilk will produce a slightly tangier dressing with a richer mouthfeel, often considered desirable in many salad dressing recipes.