Place mayonnaise, sour cream, and buttermilk in a bowl. Add garlic, black pepper, dry mustard, salt, sugar, cayenne, and Worcestershire sauce. Whisk together thoroughly.
Mix grated blue cheese into the cream base a little at a time to ensure it is evenly incorporated and doesn't clump.
Cover bowl with plastic wrap and refrigerate for at least 3 hours (preferably overnight) to consolidate the flavors.
