Preheat the oven to 350 degrees Fahrenheit. Spray a 9x9 pan with non-stick spray and line it with parchment paper.
Start by blotting your pumpkin. Spread the pumpkin puree evenly on a flat surface, like a plate or a sheet pan. Place a paper towel over the top and lightly press to absorb the excess liquid. Repeat this step at least five more times. You should have slightly over ⅓ cup of pumpkin puree. Alternatively, you can use a cheesecloth to squeeze out the liquid, allowing the pumpkin to form a more cohesive texture, resembling play dough.
In a small bowl, combine ¼ cup of granulated sugar and 1 tablespoon of ground cinnamon for the topping. Set aside.
In a medium bowl, whisk together the flour, pumpkin pie spice, ground cinnamon, baking soda, baking powder, and salt. Set aside this dry mixture.
In another medium-sized bowl, using a whisk, 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 egg and egg yolks one at a time, each time whisking by hand for about 30 seconds. After incorporating the eggs, add the vanilla extract and the prepared pumpkin puree. Whisk just until the ingredients are combined.
Switch to a rubber spatula and gently fold the dry flour mixture into the wet batter. Mix until there are no longer any visible signs of flour, being careful not to overmix.
Pour the batter into the prepared pan, spreading it evenly.
Sprinkle the cinnamon sugar topping over the batter, ensuring the entire surface is covered.
Bake the blondies for 35-38 minutes, 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 in the pan for 15 minutes, preferably on a wire rack. If desired, you can also sprinkle extra white chocolate chips over the top during this cooling period.
Afterward, let the blondies cool completely before cutting and serving.
Notes
This is really important! You need to make sure that you remove the moisture from the pumpkin or else your blondies will result in a more cake like texture and not chewy cookie texture. You can also use a cheesecloth to remove the moisture. This can take some time to do, but if you do it right you will have the best chewy texture.