In a medium bowl, place about 1-2 oz of blue cheese crumbles along with the buttermilk. Use a fork to smush the blue cheese crumbles. It doesn’t have to be completely smooth, just so they are not large crumbles.
Add in the mayonnaise, sour cream, lemon juice, parsley, salt and pepper to the bowl and stir to combine.
*Optional* Reserve a tablespoon of blue cheese crumbs to top your dressing with as additional garnish. Fold in the remaining blue cheese crumbles. Refrigerate and allow to sit for at least 30 minutes.
Notes
How to make dressing thinner:
If you would like your dressing a little thinner, then add buttermilk a teaspoon at a time. If you would like your dressing more acidic than instead of additional buttermilk, you can add additional lemon juice or even white vinegar a teaspoon at a time.