Buttermilk Ranch dressing

I've always loved ranch dressing, but this is way better than the store-bought stuff. And super easy to make, too.

1 1/2 C. mayonnaise  OR sour cream  (Sour cream makes it a little more mild.
1 tsp. onion powder
1 tsp. garlic powder
2 tsp. dried parsley  (you can use fresh parsley chopped fine)
1 1/2 C. buttermilk
Salt and Pepper to taste

Whisk together all ingredients in a medium bowl.  Let stand in the fridge a few hours before serving .