julie,

just something i got from the internet. hope this helps. have a great weekend!
GREEN GODDESS DRESSING
( about 2 cups )

1 to 1 1/4 cups mayonnaise
1/2 cup (4 oz.) sour cream or sour half and half
1 1/2 tablespoons snipped fresh parsley
1/4 cup minced green onions with tops
2 tablespoons lemon juice or tarragon or wine vinegar
1/2 clove garlic, minced
1/2 teaspoon salt, optional
Dash ground pepper
In medium bowl, stir together all ingredients until well combined. Cover and chill if not using immediately.