01 - Line a 23x23 cm baking pan with parchment paper, ensuring an overhang for easy removal.
02 - In a bowl, combine the crushed chocolate sandwich cookies and melted butter. Press this mixture firmly and evenly into the bottom of the prepared pan to create the base. Refrigerate while preparing the next layer.
03 - Melt the dark and milk chocolate together using a double boiler or in short intervals in the microwave, stirring until completely smooth. Incorporate the peppermint extract.
04 - Pour the melted chocolate mixture evenly over the chilled cookie base. Distribute the mini marshmallows, crushed peppermint candies, and broken cookies over the chocolate, gently pressing them into the surface.
05 - Drizzle the melted white chocolate over the toppings in a decorative zigzag pattern.
06 - Refrigerate the bars for a minimum of 2 hours, or until they are completely firm.
07 - Once set, use the parchment overhang to lift the slab from the pan. Cut into individual bars before serving.