In a small mixing bowl, whisk together the buttermilk and mayonnaise until smooth. Stir in the blue cheese crumbles and scallions. Season to taste with salt and pepper.
Chill the dressing to allow the flavors to blend. Use within 4 days.
Notes
Promptly store leftovers in an airtight container in the refrigerator, for up to 4 days.Nutritional values are approximate and based on 1 tablespoon.
You DO need real buttermilk, not the dried powder, not the add-vinegar-to-milk stuff. If in a pinch, mix equal parts of yogurt and milk for a reasonable buttermilk substitute.
Blue cheese or gorgonzola crumbles will both work in this recipe, but for the freshest and best-tasting cheese, buy it in a block and crumble it yourself. Freeze extra cheese for another time.
You can experiment with other aromatics besides the scallions. Add in your favorite herbs if you like, such as dill or basil.