Preheat your oven to 350°F. Line a large rimmed baking sheet with parchment paper and set it aside.
In a large mixing bowl, place the oat flour, baking soda, salt, pumpkin spice, granulated sugar, brown sugar, and oats, and mix to combine well. Break up any lumps in the brown sugar.
Add the butter, and mix with the back of the spoon until it’s evenly distributed throughout the dry ingredients. The mixture should look like coarse, slightly wet sand.
Create a well in the center of the dry ingredients, and add the pumpkin butter and egg, and mix to combine. The dough will be very thick and relatively sticky.
Mix in the optional chocolate chips until evenly distributed throughout the cookie dough.
Divide the dough into 10 equal portions, each about 50 grams. I used a medium ice cream scoop.
Place the portions on the prepared baking sheet about 1 1/2 inches apart from one another. If the mounds of raw dough seem misshapen, roll each piece of chilled dough into a round between clean, moistened palms and replace on the baking sheet. The dough will be thick, and very sticky.
Bake in the center of the preheated oven until lightly golden brown all over, golden brown around the edges, and no longer wet in the center (about 12 minutes).
Remove from the oven and allow to cool until set on the baking sheet (about 10 minutes) before serving.
Notes
About pumpkin butterIf you don't have pumpkin butter and don't want to buy or make it, you can substitute 100 grams of canned pumpkin puree blotted of extra moisture with paper towels until it weighs 65 grams + 2 tablespoons (42 grams) pure maple syrup + 1 extra teaspoon pumpkin pie spice for a total of 2. The cookies will be thicker and more cakey, and will take longer to bake (about 17 minutes).