3 green onions white and green parts, chopped
½ cup chopped fresh basil leaves, lightly packed
2 tablespoons freshly squeezed lemon juice
1½ tablespoons Dijon mustard
1 tablespoon olive oil
2 garlic cloves, chopped
2½ teaspoons kosher salt
1 teaspoon freshly ground black pepper
1 cup mayonnaise
½ cup Greek yogurt
½ cup buttermilk, well shaken
Place the green onions, basil, lemon juice, Dijon, olive oil, garlic, salt and pepper in the bowl of a food processor. Pulse until the mixture is smooth, about 15 to 20 seconds. Add the remaining ingredients and puree until smooth.
Transfer to an airtight container and refrigerate for at least an hour before serving to let the flavors develop.