01 -
Line an 20 cm x 20 cm baking pan with parchment paper crisscrossed to create a 5 cm overhang on all sides. Lightly grease with cooking spray.
02 -
In a medium heatproof bowl, microwave semisweet chocolate chips, sweetened condensed milk, and chopped bittersweet chocolate in 30-second intervals, stirring between, until smooth and melted, approximately 90 seconds total. Transfer mixture to a medium pot.
03 -
In a small bowl, stir together marshmallow fluff, espresso powder, unsalted butter, and Kahlúa. Scrape into the pot with melted chocolate. Cook over medium heat, stirring continuously, until heated through, about 1 minute. Pour the mixture into the prepared pan and smooth the surface. Wipe out the pot.
04 -
In a medium heatproof bowl, microwave white chocolate chips and sweetened condensed milk in 30-second increments, stirring between, until melted and smooth, about 90 seconds total. Transfer to the reserved pot.
05 -
In a small bowl, mix marshmallow fluff, unsalted butter, Baileys Irish Cream, and Kahlúa. Scrape this mixture into the pot with the melted white chocolate. Cook over medium heat, stirring constantly until warmed through, about 1 minute. Pour the top layer mixture evenly over the bottom layer and smooth the surface.
06 -
Refrigerate until set, a minimum of 2 hours and up to 5 days. Using the parchment overhang, lift the fudge from the pan and transfer to a cutting board. Dust the surface with espresso powder, cut into squares, and garnish with espresso beans if desired.