01 - Line an 8x8-inch baking pan with parchment paper, leaving an overhang on opposite sides for easy removal later.
02 - Combine chocolate cookie crumbs and melted butter in a medium bowl. Mix until evenly moistened and press firmly into the bottom of the prepared pan to form an even layer. Set aside.
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. Remove from heat.
04 - In a large bowl, beat the softened cream cheese with an electric mixer until completely smooth and creamy, about 2 minutes.
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 uniform color is achieved.
06 - Pour the cheesecake fudge mixture over the prepared crust. Spread evenly with a spatula. Refrigerate for at least 3 hours or until completely set and firm.
07 - Once set, drizzle melted dark chocolate over the top using a spoon or piping bag. Immediately sprinkle with green decorations if desired.
08 - Using the parchment overhang, lift the fudge out of the pan. Cut into 16 equal squares with a sharp knife, wiping the blade clean between cuts for neat edges.