Ingredients

1/2 cup sour cream 

1/3 cup mayonnaise 

1 anchovy fillet, rinsed and patted dry 

3/4 cup lightly packed fresh flat-leaf parsley leaves 

1/4 cup lightly packed fresh basil leaves 

2 scallions, white and pale-green parts separated from dark-green tops 

Coarse salt and freshly ground pepper 

2 tablespoons lightly packed chopped fresh tarragon leaves 

Crudites or crostini, for serving 

Preparation

Combine sour cream, mayonnaise, anchovy, parsley, basil, white and pale-green parts of scallions, 1/2 teaspoon salt, and a pinch of pepper in a food processor and puree until smooth. Transfer to a bowl.

Finely chop scallion tops and stir into dressing along with tarragon. Season with salt and pepper and serve with crudites or crostini.