1. Sift flour, baking powder, sugar, and salt into a large bowl.

2. In medium bowl, whisk together yolks, milk, melted butter, and vanilla until combined. Whisk yolk mixture into flour mixture until just combined; batter will be slightly lumpy.

3. Place egg white in the bowl of an electric mixer fitted with the whisk attachment, or whisk by hand, until medium peaks form. Gently mix half the egg whites into batter with a rubber spatula. Gently fold in remaining whites. The egg whites should not be fully incorporated into the batter.

4. Heat a griddle until hot, about 350 to 375 degrees. Add remaining unmelted butter to hot griddle. Add 1/4 cup pancake batter and let set. Sprinkle 1 tablespoon blueberries or sliced bananas and 1 teaspoon chopped walnuts, if using, over pancakes. When bubbles begin to form, lift pancake; if golden brown, turn. Cook until golden brown on remaining side.

5. Transfer cooked pancake to a plate and keep warm. Repeat process with remaining batter, fruit, and nuts. Garnish with confectioners' sugar for blueberry pancakes and cinnamon sugar for banana-walnut. Serve warm with maple butter.