01 - Line a 9x9-inch square pan with parchment paper and lightly grease the surface.
02 - In a large saucepan over low heat, melt the butter. Add Biscoff spread and stir until smooth and completely combined.
03 - Add mini marshmallows to the saucepan and cook, stirring constantly, until melted and homogeneous.
04 - Remove saucepan from heat. Fold in Rice Krispies cereal until every grain is evenly coated with the mixture.
05 - Use a greased rubber spatula or wax paper to gently and evenly press the mixture into the prepared pan.
06 - Drizzle melted Biscoff spread over the surface and sprinkle with crushed Biscoff cookies if desired.
07 - Allow to cool at room temperature for about 45 minutes or until thoroughly set. Cut into 16 equal squares and serve.