In a large bowl, whisk together the flour, sugar, baking powder, pumpkin pie spice, and salt.
In a separate bowl, combine the milk, pumpkin puree, egg yolks, melted butter, and vanilla extract together, whisking to blend until smooth.
Add the wet ingredients to the dry ingredients, mixing with a spatula until just combined.
In the bowl of an electric mixer, beat the egg whites until thick and stiff.
Gently fold the egg whites into the pancake batter until fully incorporated.
Meanwhile, heat a frying pan over medium heat.
Lightly spray the pan with cooking spray or use butter or butter substitute (we like Brummel & Brown). Pour batter onto pan in 1/4-cup increments (I like scooping it with a 1/4 cup measuring cup and using the bottom of the cup to smooth out the thick batter).
Cook each pancake until lightly browned on each side, about 1 minute per side. Air bubbles will start to reach the surface of the pancake and escape, indicating that it may be time to flip.
Transfer each cooked pancake to a warm plate (or one in the microwave to prevent cooling) and repeat with the remaining batter.
Serve with your favorite pancake toppings.