Preheat the oven to 350°F and lightly grease a 12-count muffin tin.
Scoop about two tablespoons of cookie dough into each muffin cup and press the dough gently up the sides to form a cup.
Bake for 10 to 12 minutes, or until golden brown.
As soon as they come out of the oven, press the centers down with the back of a spoon to make the cups deeper, then let them cool completely in the pan before removing.
While the cookie cups cool, prepare the Oreo buttercream. Beat the stick of salted butter until smooth, then add the powdered sugar, heavy cream, Oreos, and vanilla. Mix until light and fluffy, adjusting the cream as needed for consistency.
Transfer the frosting to a piping bag and fill each cooled cookie cup with a swirl. Decorate the tops with Halloween confetti and toppers.