01 - Line a 9x9-inch square pan with parchment paper and lightly grease the surface.
02 - In a large saucepan set over low heat, melt the butter. Stir in 1 cup Biscoff spread and mix until completely smooth.
03 - Add mini marshmallows to the saucepan. Cook, stirring constantly, until marshmallows are fully melted and well combined with the mixture.
04 - Remove the pan from heat. Gently fold in the Rice Krispies cereal until each grain is thoroughly coated.
05 - Transfer the mixture to the prepared pan. Using a greased spatula or wax paper, press the mixture gently and evenly across the pan.
06 - Drizzle melted Biscoff spread over the surface and sprinkle with crushed Biscoff cookies, if desired.
07 - Allow the treats to cool at room temperature for approximately 45 minutes, or until fully set.
08 - Cut into 16 equal squares for serving.