01 -
In a large bowl, cream together the butter and granulated sugar until light and fluffy. Beat in the egg and vanilla. In another bowl, whisk together the flour, cocoa powder, baking soda, and salt. Gradually add to the creamed mixture alternating with the milk until well combined.
02 -
Wrap the dough in plastic wrap and refrigerate for at least 1 hour.
03 -
Preheat the oven to 175°C. Line baking sheets with parchment paper.
04 -
Roll the dough into balls, then flatten slightly on the prepared baking sheets. Bake for 10 minutes, or until the cookies are set but still soft. Allow to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.
05 -
Beat together the butter, powdered sugar, vanilla extract, and heavy cream until smooth and fluffy. Fold in the crushed Oreo pieces.
06 -
Once the cookies have cooled completely, spread or pipe the filling onto the flat side of one cookie and then top with another cookie to make a sandwich.