Preheat the oven to 400 degrees F. Line the bottom of a 9X13-inch baking pan with parchment paper and lightly grease with nonstick cooking spray. Set aside. *I've only used a metal baking pan for this recipe; if using glass, the pancake may bake faster.
In a medium bowl, whisk together the buttermilk, egg, and butter. Add the flours, sugar, baking powder, baking soda, and salt. Whisk until just combined and no dry streaks remain (it's ok if the batter has small lumps).
Spread the batter evenly in the pan; it will be a thin layer. If desired, top the batter with 1 cup fresh berries (could try frozen, too), and sprinkle with coarse sugar.
Bake for 15-20 minutes until puffy and lightly golden on the edges; the top of the pancake will spring back lightly when gently pressed. Serve warm or at room temperature with butter, syrup, jam or other pancake toppings.
Flour: I prefer using white whole wheat flour; it lends a lighter texture to the pancake batter than red whole wheat flour.