Rinse and drain fresh blueberries.
In a bowl, mix buckwheat flour with cornmeal, all-purpose flour, sugar, baking powder, and baking soda. Add egg yolks and buttermilk; stir just until batter is evenly moistened. Add blueberries.
In a deep bowl, whip egg whites with a mixer on high speed just until whites hold stiff peaks. Gently fold whites into batter.
Place a nonstick griddle or 11- to 12-inch nonstick frying pan over medium heat. When hot, pour batter, about 1/4 cup for each cake, onto griddle. Cook until tops of pancakes are bubbly and edges appear dry, 1 to 1 1/2 minutes. Turn over to brown other side.
Serve hot with butter and syrup.