1In a small bowl, whisk the flour, baking powder and salt. In a large bowl, whisk the egg yolks with the milk, ricotta, sugar and vanilla.
2Add the dry ingredients and whisk until the batter is smooth.
3In a large bowl, using an electric mixer, beat the egg whites at medium speed until frothy. Beat at high speed until soft peaks form. Fold the egg whites into the batter until no streaks remain.
4Preheat the oven to 225°.
5Heat a griddle, then lightly butter it. For each pancake, ladle a scant 1/4 cup of the batter onto the griddle; be sure to leave enough space between the pancakes. Cook over moderately low heat until the bottoms are golden and the pancakes are just beginning to set, 1 to 2 minutes.
6Sprinkle each pancake with a few blueberries and press lightly. Flip the pancakes and cook until golden on the bottom and cooked through, about 1 minute longer.
7Transfer the pancakes to plates and keep them warm in the oven while you make the rest. Serve the pancakes with maple syrup.