Preheat oven to 200°F. In a large bowl, whisk together the all-purpose flour, whole wheat flour, sugar, baking powder, baking soda, and salt; set aside.
In a small bowl, combine buttermilk, egg, oil, and vanilla. Whisk to combine.
Add buttermilk mixture to the flour mixture. Stir just until moistened (batter will be lumpy). Transfer batter to a pancake pen, if using.
Stick a large pan or griddle set over medium heat with butter or oil. Once hot, add batter to the pan. If using a pen, pour batter in X and O shapes. Otherwise, make round pancakes (you'll cut the X's and O's later). Cook the pancakes for 2-3 minutes or until the surfaces are bubbly and edges are slightly dry. Flip and cook on the second side until lightly browned, 2-3 minutes. Place cooked pancakes on an ovenproof plate and store in the warmed oven until ready to serve. If desired, sprinkle with powdered sugar.
How did we get such perfect letters? A pancake pen! We like the one from Tovolo.