In a medium bowl or large measuring cup, add the mayonnaise, Greek yogurt (or sour cream), and buttermilk. Whisk until completely smooth and creamy with no lumps.
1/2 cup mayonnaise, 1/4 cup plain Greek yogurt or sour cream, 1/4 cup buttermilk
Add the extra-virgin olive oil, white wine vinegar, and lemon juice. Whisk again until well combined and slightly thickened.
3 tablespoons extra-virgin olive oil, 3 tablespoons white wine vinegar, 1 tablespoon lemon juice
Whisk in the Dijon mustard, honey or sugar, grated Parmesan, garlic powder, onion powder, kosher salt, black pepper, and crushed red pepper flakes if using, until the dressing is smooth and the Parmesan is evenly distributed.
2 tablespoons Parmesan cheese, 2 teaspoons honey or sugar, 1 1/2 teaspoons Dijon mustard, 3/4 teaspoon garlic powder, 1/2 teaspoon onion powder, 1/2 teaspoon kosher salt, 1/4 teaspoon black pepper, 1/4-1/2 teaspoon crushed red pepper flakes
Stir in the finely minced fresh garlic. Sprinkle in the dried oregano, dried basil, and dried parsley, rubbing the dried herbs between your fingers as you add them to release their oils. Whisk until the herbs are evenly speckled throughout. If using fresh parsley, add it now.
1 1/2 teaspoons dried oregano, 1 teaspoon dried basil, 1 teaspoon dried parsley, 1 small clove fresh garlic
Check the texture. For salad, the dressing should slowly run off a spoon. If it is too thick, whisk in 1–2 tablespoons of water or extra buttermilk at a time until it reaches your preferred consistency.
2-3 tablespoons water or extra buttermilk
Taste the dressing on a piece of lettuce. Adjust with more salt for punch, lemon for brightness, honey for balance, or garlic for a sharper edge as desired.
1 tablespoon lemon juice, 2 teaspoons honey or sugar, 1 small clove fresh garlic, 1/2 teaspoon kosher salt
Transfer the dressing to a glass jar or airtight container. Refrigerate for at least 30 minutes and up to 1–2 hours before serving to allow the flavors to meld.
Shake the jar or stir the dressing before serving. Drizzle over salads, toss with cooked and cooled pasta, spoon over roasted vegetables, or use as a marinade for chicken.