This recipe is from roxlet from my Chowhound days. It is my favorite
1 cup mayonaise (reduced fat is OK)
1 tablespoon fresh lemon juice
1 clove of garlic finely chopped
1 tablesppon tarragon vinegar (or use white wine vinegar with a tiny dash of taragon)
1/4 cup finely chopped green onions
1/4 cup chopped parsley
1/2 cup sour cream
4 anchovies, chopped
freshly ground black pepper
Put all the ingredients except the sour cream into a blender. Blend until all ingredients are well amalgamated. Remove to a bowl and stir in the sour cream. Do not blend with the sour cream.