Cut ½ inch off the bottom (root end) of each head of endive. Separate the leaves and keep under a damp paper towel in the refrigerator until ready to use, up to 4 hours.
Make the dressing if using. Whisk all ingredients together in a small bowl or a glass jar with a lid. This will make too much dressing for the hors d’oeuvre. Save what you don’t use for a salad.
Fill the white part of each endive leaf with a bite size crumble of blue cheese, a half of a grape and a pinch of chopped nuts. Drizzle with a touch of dressing if desired.