Heat oven to 340°F (170°C) and fold a 7.9 in (20 cm) loaf pan with parchment paper or grease with oil.
In a large mixing bowl, combine pumpkin puree with egg, egg whites, Greek yogurt, maple syrup, nut butter, vanilla extract, homemade pumpkin spice mix and salt. Stir with a whisk or fork for about two minutes, or until all is well combined and you get a smooth batter.
Mix in oat flour and baking powder. When the flour is incorporated into the wet mixture, scoop in protein powder and gently give it a stir. Do not over-mix protein powder.
Fold through the chocolate chips, if using.
Pour the batter into your prepared loaf pan. Bake in hot oven for 30 to 40 minutes, or until a toothpick inserted into the center of your protein pumpkin bread comes out clean.
Remove from oven and let cool in the loaf pan for a few minutes. Finally, remove from the pan and let cool completely.