Add yogurt, applesauce, sugar and vanilla to egg yolks. Stir with a rubber spatula to mix, then stir in baking soda, salt and flour until blended.
Beat egg whites with an electric mixer until stiff peaks form when beaters are lifted. Stir 1/3 the whites into the batter until blended. Gently fold in remaining whites until no white streaks remain.
Meanwhile heat griddle or large skillet over medium heat until a few drops of water flicked onto the surface skitter around then disappear. Wipe vegetable oil over cooking surface with a paper towel. For each pancake, pour 1/4 cup batter onto griddle or skillet, gently spreading batter to make a 4-inch pancake.
Sprinkle some blue berries on top, then cook 2 minutes longer or until bubbles appear on surface of pancake and undersides are golden brown. Turn pancakes over with a broad metal spatula and cook until tops bounce back when touched, about 2 minutes.