01 - Line an 8x8-inch baking pan with parchment paper, leaving an overhang on opposite sides for easy removal later.
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.
03 - Place white chocolate chips in a heatproof bowl set over a pan of simmering water, creating a double boiler. Stir constantly until completely melted and smooth.
04 - In a separate large bowl, beat the softened cream cheese with an electric mixer until completely smooth and creamy, with no lumps remaining.
05 - Add the melted white chocolate, sweetened condensed milk, Irish cream liqueur, peppermint extract, and salt to the cream cheese. Beat on medium speed until thoroughly combined and silky. Add green food coloring drop by drop if desired, mixing until color is uniform.
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 set and firm to the touch.
08 - Once set, drizzle melted dark chocolate over the surface and immediately sprinkle with green decorations if using.
09 - Lift the entire slab from the pan using the parchment paper overhang. Place on a cutting board and cut into 16 equal squares using a sharp knife, wiping the blade clean between each cut for neat edges.