Start by sifting together the gluten-free flour, corn starch, milk powder (if using), cream of tartar, baking soda, salt, pumpkin spice and ground cinnamon in a bowl and set aside.

In the bowl of your stand mixer, combine the room temperature butter, shortening, brown sugar, granulated white sugar and vanilla and mix for 5 minutes at medium-high speed until light and fluffy. Halfway through, pause to scrape the bowl and beater with a flexible spatula.

Add the egg yolk and mix until fully incorporated. Scrape down the sides.

Mix in the pumpkin puree.

With the mixer running on low, add your dry ingredients and mix until the wet ingredients are fully incorporated.

Place your mixing bowl in your refrigerator for 30 minutes to allow your dough to firm up.

When ready to bake, preheat your oven to 350F.

Line two sheet trays with parchment paper.

Scoop 2 tablespoon sized balls of cookie dough and roll them into balls. Roll them in the pumpkin spice sugar, then place no more than 6 of them on the prepared cookie sheets. You should get 10-12 cookies out of this dough weighing around 55-60g

Gently pat down the dough balls.

Bake them on tray at a time at 350F for 10 minutes or until they look puffy. Remember if you make them smaller, they will bake faster.

Remove the pumpkin snickerdoodles from the oven and allow them to cool for 10 minutes on the sheet tray before transfering them to a cooling rack. The cookies will deflate - that is completely normal.

Store the cookies in an air tight container at room temperature for up to 3 days.