Preheat oven to 425 degrees F.
Combine flours, baking powder, and sugar in a bowl. Cut in butter until mixture resembles fine crumbs. Beat cream and egg yolk together and add to dry ingredients. Stir with a fork just until dry ingredients are moistened.
Gently fold in blueberries with rubber scraper. Turn out on a floured surface and knead gently about six times to form a ball. Pat dough into a circle about 3/4-inch thick. Carefully place on greased baking sheet. Mark off eight wedges with a sharp knife. Be careful not to cut all the way through. Sprinkle with sugar. Bake for 20 minutes or until browned.
Break into wedges and serve hot with butter.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.