Preheat your oven to 350 degrees Fahrenheit. Grease a 9×9 inch baking pan with non-stick spray and line it with parchment paper. Set asdide
Begin by removing excess moisture from the pumpkin puree. Place the pumpkin puree in a cheesecloth and squeeze out the liquid into a small bowl. Repeat this process a couple of times to achieve a thicker, more cohesive texture, resembling play dough. Discard the pumpkin water.
In a medium bowl, whisk together the all-purpose flour, pumpkin pie spice, ground cinnamon, baking soda, baking powder, and salt. Set aside this dry mixture.
In another medium-sized bowl, using an electric hand mixer, beat the melted butter, brown sugar, and granulated sugar together until the mixture becomes light and fluffy. This should take about 3 minutes.
Whisk in the large egg and egg yolk one at a time, mixing each for about 30 seconds. After incorporating the eggs, add the vanilla extract and the prepared, well-drained pumpkin puree. Mix on low just until the ingredients are combined.
Switch to a rubber spatula and gently fold the dry flour mixture and chocolate chips into the wet batter. Mix until there are no longer any visible signs of flour, being careful not to overmix. The dough will have a somewhat thick consistency.
Pour ¾ of the dough into the prepared pan, spreading it evenly. Then, evenly spread the marshmallow fluff on top of the dough, leaving about ½ inch from all sides. Finish by topping with the remaining pumpkin dough. Add a few chocolate chips and two or three dollops of marshmallow fluff for a finished look.
Bake the blondies for approximately 25-30 minutes or until the center is slightly puffy and a toothpick inserted into the center comes out with just a few moist crumbs.
Allow the blondies to cool completely in the pan before cutting and serving.