Preheat oven to 350 degrees and line a 8x8” baking dish with parchment paper.
Melt butter and set aside to cool. Chop dark chocolate and set aside.
In a medium mixing bowl, combine all dry ingredients including flour, oat flour, oats, pumpkin pie spice, baking soda and salt. Set aside.
Combine egg, pumpkin and vanilla in another medium mixing bowl. Set aside.
Mix melted butter and sugar together in a small mixing bowl. Add 1 cup to the dry ingredients and mix until combined then press into the bottom of the baking dish.
Add the rest of the butter-sugar mixture to the pumpkin mixture, stir in the dark chocolate and then spread on top of the flour mixture in the baking dish.
Bake for 35-40 minutes until set and edges darken. Transfer dish to a wire rack to cool completely before cutting.