This recipe is from the Sullivan's Steakhouse, via Gourmet magazine. They suggest you chill overnight for flavors to develop. I can't wait and usually use it right away, though I make enough to have it on hand for several days. This is one dressing that works great on iceberg lettuce. I leave out the garlic and when I don't have buttermilk, I've thinned the dressing with a few tablespoons of regular milk or even water and it's still delicious.