Preheat the oven: Preheat the oven to 350°F and line a baking sheet with parchment paper so the cookies don't stick.

Whisk the wet ingredients: In a large bowl, whisk together the pumpkin puree, melted coconut oil, egg, and maple syrup until smooth and glossy.

Add dry ingredients: Stir in the oats, whole wheat flour, baking soda, pumpkin pie spice, cinnamon, and salt, folding just until no dry streaks remain.

Fold in mix-ins: Gently fold in the chocolate chips or chopped walnuts so they're evenly distributed through the thick dough.

Rest the dough: Let the dough rest on the counter for 10 minutes so the oats absorb moisture and thicken slightly, making it easier to scoop.

Scoop the cookies: Drop rounded tablespoons of dough onto the prepared baking sheet, spacing them about 2 inches apart.

Flatten each cookie: Press each scoop down gently with the back of a spoon, since this dough barely spreads on its own.

Bake until golden: Bake for 11 to 13 minutes, until the edges turn light golden and the centers look just set.

Cool on the pan: Let the cookies cool on the baking sheet for 5 minutes, since they're fragile straight from the oven.

Transfer to a rack: Move the cookies to a wire rack to finish cooling completely before storing.