Stir together buckwheat flour, whole wheat flour, sugar, baking powder, baking soda, and salt in a medium bowl, and then combine buttermilk, egg product, oil, and vanilla in a small bowl.
Add buttermilk mixture all at once to flour mixture. Stir just until combined but still slightly lumpy. Stir in blueberries.
Heat a lightly greased griddle or heavy skillet over medium heat until a few drops of water sprinkled on griddle jump across the surface. For each pancake, pour a scant 1/4 cup of the batter onto hot griddle. Spread batter into a circle about 4 inches in diameter.
Cook over medium heat until pancakes are browned, turning to cook second sides when pancake surfaces are bubbly and edges are slightly dry (1 to 2 minutes per side).
Serve immediately or keep warm in a loosely covered ovenproof dish in a 300 degrees F oven.