01 - Line an 8x8-inch baking pan with parchment paper, leaving an overhang on opposite sides for easy removal of the squares.
02 - In a medium bowl, combine chocolate cookie crumbs and melted butter. Mix until evenly moistened. Press the mixture firmly into the bottom of the prepared pan to form an even crust layer. Set aside.
03 - Set up a double boiler by placing a heatproof bowl over a pan of simmering water. Add white chocolate chips and stir until completely melted and smooth. Remove from heat.
04 - In a large bowl, beat the softened cream cheese with an electric mixer until smooth and creamy, about 2 minutes.
05 - Pour the melted white chocolate into the cream cheese. Add sweetened condensed milk, Irish cream liqueur, peppermint extract, and salt. Beat on medium speed until fully incorporated and silky smooth, about 2 minutes. Add green food coloring drop by drop if desired, mixing until uniform in color.
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 and set throughout.
08 - Once fully set, remove from refrigerator. Drizzle melted dark chocolate over the top in a decorative pattern and immediately sprinkle with green decorations while chocolate is still wet.
09 - Using the parchment overhang, lift the fudge block out of the pan. Place on a cutting board and cut into 16 equal squares with a sharp knife, wiping the blade clean between cuts for neat edges.