Preheat the oven to 350F. Line two or more half sheet pans with silicone baking mats and set aside.

Whisk together the dry ingredients, gluten-free flour, cocoa powder, baking powder, baking soda and salt in a medium bowl. Set aside.

In a large bowl of an electric stand mixer fitted with the paddle attachment (or with a handheld electric mixer), cream together the butter, brown sugar and granulated sugar until well-combined and creamy, 1 to 2 minutes. Scrape down the sides of the bowl as needed.

Add the eggs, sour cream and vanilla extract, and mix until thoroughly combined, scraping down the sides of the bowl as needed.

With the mixer running on low, slowly add the the dry ingredients in 3 additions, mixing well after each addition. Mix in the oreo crumbs (except the ¼ cup reserved for topping the cookies after baking).

Measure out 1/4 cup portions of dough and roll into balls. Place several inches apart on prepared baking sheets (because these are larger cookies, I only place six cookies on each half sheet pan). Flatten slightly and smooth edges before baking.

Bake for 11-13 minutes until edges are set but middles are still slightly soft. Remove from the oven and let cool on the baking sheet for a few minutes before transferring to a wire cooling rack to cool completely. If the centers are mounded, gently press with a spatula or flat-bottomed class to an even thickness.

Make the Frosting: In a large bowl of an electric stand mixer fitted with the paddle attachment (or with a handheld electric mixer) cream together the butter and cream cheese until very smooth, 1 to 2 minutes. Add the vanilla and mix until combined. Gradually add the powdered sugar, mixing on low speed, until all the sugar has been incorporated. Add a few tablespoons of milk or cream to thin out the frosting if needed. It should be thick and creamy, but also soft and easily spreadable.

Once the cookies have cooled completely, frost each cookie with an offset spatula or frost with a piping bag fitted with a round open tip and spiral the frosting in rounds over the top of the cookie. Sprinkle the cookies with Oreo cookie crumbs. Refrigerate frosted cookies until serving. Enjoy!