In a large bowl, whisk the flour, brown sugar, whey protein, baking powder, baking soda, pumpkin pie spice and cinnamon.
Add the pumpkin puree, milk and egg. Whisk to combine.
Pour the batter into a lightly oiled waffle maker on medium-low heat and cook according to the waffle maker directions. Take care not to over-fill the waffle maker, or you may have overflow once the batter puffs up.
Remove waffles from the waffle iron and enjoy right away, or store in the refrigerator in an airtight container for up to 4 days.
To freeze, place cooled waffles on a baking sheet and place in the freezer. Once firm, transfer waffles to a freezer-safe bag and store for up to 3 months.