01 - Line an 8x8-inch baking pan with parchment paper, allowing overhang on opposite sides for easy removal later.
02 - Combine chocolate cookie crumbs and melted butter in a medium bowl. Mix until uniformly moistened. Press firmly into the bottom of the prepared pan, creating an even layer. Set aside.
03 - Place white chocolate chips in a heatproof bowl set over a pan of simmering water. Stir constantly until completely smooth and melted. Remove from heat.
04 - In a large bowl, beat softened cream cheese with an electric mixer until completely smooth and creamy, about 2 minutes.
05 - Add melted white chocolate, sweetened condensed milk, Irish cream liqueur, peppermint extract, and salt to the cream cheese. Beat until thoroughly combined and silky. Add green food coloring drop by drop if desired, mixing until color is even.
06 - Pour the cheesecake fudge mixture over the prepared crust. Use a spatula to spread evenly and smooth the top surface.
07 - Refrigerate for at least 3 hours or until completely firm throughout. The fudge should hold its shape when touched.
08 - Once fully set, drizzle melted dark chocolate over the surface and immediately sprinkle with green decorations if using. Return to refrigerator for 5 minutes to set the chocolate.
09 - Lift the fudge from the pan using the parchment overhang. Cut into 16 equal squares using a sharp knife, wiping the blade clean between cuts for neat edges.