In a mixing bowl, cream butter and sugar. Add eggs, buttermilk and vanilla; mix well. Combine flour, baking soda, baking powder and salt; stir into the creamed mixture just until moistened. Fold in blueberries (batter will be thick).
Fill greased or paper-lined miniature muffin cups with about a tablespoon of batter. Sprinkle with sugar if desired. Bake at 400 degrees F for 10-15 minutes or until a toothpick comes out clean. Cool for 5 minutes before removing from pan to a wire rack