Preheat your oven to 350°F. Line rimmed baking sheets with unbleached parchment paper and set them aside.
In a small bowl, place the flour, xanthan gum, baking soda, salt, and pumpkin pie spice, and whisk to combine well. Set the bowl aside.
Place the pumpkin puree on a small, flat plate and spread it into a thin, even layer. Using paper towels, blot the puree to absorb all excess moisture, pressing down gently and evenly. You will use and discard about 8 layers of paper towel, two layers at a time.
Keep blotting until the volume of the puree has reduced by nearly half (it should ultimately weigh about 2 ounces). There will still be more moisture if you continue to press with a paper towel, but the puree should darken in color and its texture should go from fluffy to almost crumbly.
Place the granulated sugar, brown sugar and butter in a large mixing bowl, and beat with a handheld mixer (or in the bowl of a stand mixer fitted with the paddle attachment) for about 5 minutes or until light and fluffy.
To the butter and sugars mixture, add the dried pumpkin puree, egg yolks, and vanilla, and beat until fully combined.
Add the dry ingredients and mix by hand with a spoon. Press the mixture with the back of the bowl of the spoon to get all of the dry ingredients moistened by the wet ingredients. The dough may seem too dry at first to absorb all the dry ingredients, but keep pressing and it will come together.
Add the chocolate chips. Mix until they’re evenly distributed throughout the cookie dough.
Using a medium-size ice cream scoop or two spoons, place rounded portions of the dough (each about 2 tablespoonsful) on the prepared baking sheet, about 1 1/2-inches apart.
Place the baking sheet in the center of the preheated oven and bake until the cookies are lightly golden brown around the edges and set in the center, about 15 minutes.
Remove from the oven and allow to cool on the baking sheet until firm, about 10 minutes.
Notes
For the flour blend.I really like using Nicole's Best multipurpose gluten free flour blend, with added 3/8 teaspoon xanthan gum, to make these cookies. Better Batter's classic blend also works well, as does Bob's Red Mill 1-to-1, with 1/8 teaspoon added xanthan gum.They've changed the formula for Cup4Cup, and I can no longer recommend it. You can use any of my "mock" blends on the all purpose gluten free flour blends page.For the pumpkin pie spice.To make your own pumpkin pie spice, combine 1 teaspoon ground cinnamon + 1/2 teaspoon ground ginger + 1/4 teaspoon ground allspice, 1/4 teaspoon ground cloves + 1/8 teaspoon ground nutmeg.