01 - Line a 9x9-inch square baking pan with parchment paper and lightly grease the surface.
02 - In a large saucepan over low heat, melt the unsalted butter. Add Biscoff spread and stir until the mixture is thoroughly combined and smooth.
03 - Incorporate mini marshmallows into the butter mixture and cook, stirring constantly, until the marshmallows are fully melted and the batter is homogeneous.
04 - Remove the pan from heat. Fold Rice Krispies cereal into the melted mixture, ensuring the cereal is evenly coated.
05 - Transfer the mixture to the prepared pan. Press gently and evenly into the corners using a greased rubber spatula or wax paper.
06 - Drizzle melted Biscoff spread over the set mixture and, if desired, sprinkle crushed Biscoff cookies on top.
07 - Allow to cool at room temperature for approximately 45 minutes or until firm. Once set, cut evenly into 16 squares.