01 - Line an 8x8-inch baking pan with parchment paper, allowing paper to extend over sides for easy removal later.
02 - Combine chocolate cookie crumbs and melted butter in a medium bowl. Mix until crumbs are evenly coated. Press mixture firmly into bottom of prepared pan to form an even crust 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 chocolate is completely melted and smooth. Remove from heat.
04 - In a separate large bowl, beat softened cream cheese with 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 cream cheese. Beat on medium speed until mixture is thoroughly combined and silky, about 2 minutes. If using green food coloring, add drops and mix until color is evenly distributed.
06 - Pour cheesecake fudge mixture over prepared crust. Use spatula to spread evenly and smooth top surface.
07 - Refrigerate for at least 3 hours or until fudge is completely firm and set throughout.
08 - Once fully set, drizzle melted dark chocolate over top. Sprinkle with green decorations immediately while chocolate is wet.
09 - Using parchment paper overhang, lift fudge out of pan. Cut into 16 equal squares using sharp knife, wiping blade clean between cuts for clean edges.