Preheat the oven to 350°F and line two large baking sheets with parchment paper.
Cream the butter (2 min): To a large bowl with an electric mixer, or stand mixer fitted with the paddle attachment, beat the butter and sugar on medium-high speed until light and fluffy, 2-3 minutes.
1/2 cup unsalted butter, 1 ½ cups granulated sugar
Add the wet ingredients (3 min): With the mixer running on low, pour in the oil and mix until combined. Add the sour cream, egg, and vanilla extract and mix on medium-low speed until combined. It’s ok if it’s somewhat lumpy.
1/2 cup vegetable oil, 1 cup full-fat sour cream, 1 large egg, 1 teaspoon vanilla extract
Whisk dry ingredients (2 min): In a separate medium bowl, whisk together the baking powder, salt, cinnamon, and flour. With the mixer running on low speed, add the dry ingredients until combined.
1 teaspoon baking powder, 1 teaspoon salt, 3/4 teaspoon cinnamon, 4 1/2 cups all-purpose flour
Shape the cookies (3 min): Using a 1/4 cup (or a very large cookie scoop), scoop and roll the dough into smooth balls and place on the prepared baking sheet 3 inches apart. Use the back of a Tablespoon to create a well in to center of the cookie dough. These cookies don’t spread much so how they look going into the oven is what they’ll look like. I like to make sure my edges are as smooth as possible.
Prepare the filling (5 min): In a large bowl, whisk together all of the filling ingredients until combined and smooth.
1/4 cup pumpkin puree, 1/3 cup light brown sugar, 1/4 teaspoon salt, 1 teaspoon pumpkin pie spice, 1 teaspoon cornstarch, 1/4 cup half and half, 1 large egg
Fill the cookies (3 min): Pour the pumpkin pie filling into each cookie dough well almost all the way to the top. I like to use a small liquid measuring cup with a spout for easy pouring.
Bake the cookies (12-14 min): Bake in the preheated oven for 12-14 minutes, until the pumpkin filling is set and no longer jiggles in the center when you nudge it. Allow the cookies to cool for 5 minutes on the baking sheet then transfer to a wire rack to cool completely. You can transfer them to the fridge until they’re ready to decorate and serve (I prefer to serve them chilled, but room temp works too).
Decorate and serve (5 min): Pipe whipped cream in a back-and-forth motion on one half of the cookies and dust with cinnamon sugar.