Preheat the oven to 350°F. Line baking sheets with parchment paper.
Sift together the flour, cocoa powder, baking soda, and salt.
In a separate bowl, cream the softened butter, granulated sugar, and brown sugar until well combined and lighter in texture.
Beat in the eggs and vanilla until smooth, scraping the bowl as needed.
dd the dry ingredients and mix until no dry flour remains.
Scoop the dough, using a 1 tablespoon scooper, onto the prepared baking sheets, leaving room for spreading.
Bake for 9–11 minutes, until the edges are set and the centers still look slightly soft.
Let the cookies firm up on the baking sheets, then transfer to a rack and cool completely before icing.
Pipe or spread the milk chocolate icing onto the cooled cookies. Divide the Oreo crumbs over the tops while the icing is soft, then gently press 2 gummy worms into each cookie.
