Preheat your oven to 350°F (175°C) and line a standard 12-cup muffin tin with parchment liners or grease with coconut oil.

In a large mixing bowl, whisk together the pumpkin puree, maple syrup, eggs, melted coconut oil, and vanilla extract until the mixture is smooth and emulsified.

In a separate medium bowl, sift together the oat flour, baking powder, baking soda, pumpkin pie spice, cinnamon, and sea salt.

Gradually add the dry ingredients to the wet ingredients, stirring with a spatula until just combined. Fold in chocolate chips or walnuts if using.

Divide the batter evenly among the 12 muffin cups, filling each approximately three-quarters full.

Bake for 20 to 22 minutes, or until a toothpick inserted into the center of a muffin comes out clean with no wet batter.

Remove from the oven and allow the muffins to cool in the pan for 5 to 10 minutes before transferring them to a wire rack to cool completely.