Prepare a large baking tray or cutting board by lining it with parchment paper and set it aside for later use.
Heat the peanut butter and white chocolate chips in the microwave using a low or defrost setting. Make sure to stir frequently until the mixture is nice and smooth.
Pour the mixture into a piping bag and twist the top to seal it. Let it cool for about 5 minutes, then carefully cut a small piece off the tip. The bag should feel cool to the touch when it's ready for use.
Place the fudge striped cookie, striped side down.
Pipe the white chocolate peanut butter into the centers of the cookies, making a small circle about the size of a Reese’s miniature cup.
Place the miniature peanut butter cup on top with the larger side facing down. Lightly press it down to allow the white chocolate peanut butter to ooze out from the bottom, forming a nice band around it.
Place an M&M on the band to make a buckle.
Allow to set completely before serving. You can transfer to the refrigerator for 10-15 minutes to speed up the process. The white chocolate peanut butter will harden so the hat holds its shape. Enjoy!