Start by baking the cookies. In a medium bowl combine melted and cooled coconut oil, light brown sugar, egg yolk, pumpkin puree and vanilla extract. Whisk to combine.
In a separate bowl, whisk the oat flour, pumpkin pie spice, arrowroot powder, baking soda and salt.Add the dry ingredients to the wet ingredients and stir together until combined. Fold in the chocolate chips.
Cover the dough and refrigerate for at least one hour.
Preheat the oven to 350 degrees F. Use a cookie scoop to portion out the dough onto a baking sheet lined with parchment paper. Bake for approximately 10-12 minutes. Remove from the oven and let cool.
While the cookies are cooling, prepare the pumpkin ice cream.
In the bowl of a food processor, add the frozen bananas, pumpkin puree, and pumpkin pie spice. Pulse until a smooth and creamy consistency forms, about 5 minutes.
Place the ice cream in the freezer for about 15 minutes so that it firms up a bit more. This will make it easier to use for the ice cream sandwiches.
Once the ice cream has hardened, use a spoon to scoop it onto the bottom of one cookie. Place the second cookie on top, sandwiching the two together. Repeat with remaining pumpkin ice cream.