Preheat oven to 350°F (175°C) and line a 12-cup muffin tin with paper liners or non-stick spray.

In a large mixing bowl, whisk together the pumpkin puree, eggs, maple syrup, and almond milk until fully emulsified.

In a medium bowl, combine the oat flour, vanilla whey protein powder, pumpkin pie spice, baking powder, baking soda, and salt.

Incorporate the dry ingredients into the wet mixture using a spatula, stirring until just combined to avoid a rubbery texture.

Gently fold in the dark chocolate chips if desired.

Apportion the batter evenly into the 12 prepared muffin cups.

Bake for 18 to 22 minutes, or until a toothpick inserted into the center of a muffin emerges clean.

Transfer the muffin tin to a wire rack to cool for 5 minutes before removing the muffins to cool completely.