In a medium bowl, whisk the flour, baking powder, pumpkin pie spice, cinnamon, and salt together. Set aside.

In a large bowl using a handheld or a stand mixer fitted with a paddle attachment, beat the butter and sugar together on medium-high speed until the mixture is light and creamy, about 3 minutes. Add the egg yolk, vanilla, and blotted pumpkin and beat on medium-high speed until combined, about 1 minute. Scrape down the sides and bottom of the bowl and beat again as needed to combine. Add the dry ingredients to the wet ingredients and mix on low speed until combined. The dough should be soft. If it seems too soft and sticky for rolling, beat in 1 more Tablespoon of flour.

Divide the dough in half. Place each portion on a piece of lightly floured parchment paper or a lightly floured silicone baking mat. With a lightly floured rolling pin, roll the dough to about 1/4-inch thickness. Use a bit more flour if the dough seems too sticky. The rolled-out dough can be any shape, as long as it is evenly 1/4 inch thick.

Lightly dust one of the rolled-out dough portions with flour. (This prevents sticking.) Place the second rolled-out dough portion, still on the silicone baking mat or parchment paper, on top of the first. Cover the dough tightly and refrigerate it for at least 2 hours and up to 2 days.

Preheat the oven to 350°F (177°C). Line large baking sheets with parchment paper or silicone baking mats.

Carefully remove the top piece of dough from the refrigerator. If it’s sticking to the bottom, run your hand under it to help remove it. Using a cookie cutter, cut the dough into shapes. Gather the scraps, reroll, and continue cutting until all the dough is used. (Note: It doesn’t seem like a lot of dough, but you get a lot of cookies from the dough scraps you reroll.) Repeat with the second piece of dough. Arrange the cookies 3 inches apart on the prepared baking sheets.

Bake for 11–13 minutes or until the edges of the cookies are very lightly browned and set. If your oven has hot spots, rotate the baking sheets halfway through bake time. Allow the cookies to cool on the baking sheet for 5 minutes, then transfer to a cooling rack to cool completely before decorating.

With a handheld or stand mixer fitted with a paddle attachment, beat the butter on medium speed until creamy, about 2 minutes. Add the confectioners’ sugar, heavy cream (or half-and-half or milk), vanilla extract, pumpkin pie spice, and salt. Beat on low speed for 30 seconds, then increase to medium-high speed and beat for 2 full minutes.

Tint the buttercream with gel food coloring, or leave it white. You can spread it on with a knife or icing spatula. To pipe the frosting, fit a piping bag with a piping tip, and use a coupler if you plan to switch tips.

Divide the prepared frosting between two bowls. Tint one portion orange and leave the other white; you can also set aside a small amount to tint brown or green for the pumpkin stems. Using a Wilton 4B piping tip, pipe curved lines over each pumpkin-shaped cookie to create the ridged texture shown in the photo. I used a Wilton 21 piping tip with brown frosting for the stems.

Cover and store decorated cookies at room temperature for 1 day, or in the refrigerator for up to 5 days. Frosting “soft-sets” on the cookies after a few hours, meaning it will slightly dry on top.