Combine all ingredients in a blender or food processor. Puree until very smooth, scraping sides as needed; about 1 minute. Serve immediately or cover and store in refrigerator up to 1 week.
Recipe tip: For chunky dressing, reserve half the blue cheese. Crumble and stir in after the dressing has been pureed. For extra zing, stir in a few drops of hot pepper sauce. This dressing is also delicious served on baked potatoes.