To Make the Rice Krispies Treat garnish

1. Spray an 8×8-inch baking pan with non-stick cooking spray.
2. In a saucepan, melt butter and mini marshmallows over low heat, stirring until completely melted and well combined. Remove from heat.
3. Stir in Rice Krispies cereal and stir until well coated. Pour the marshmallow and cereal mixture into the prepared pan and using a buttered spatula or wax paper, press mixture firmly into the pan.
4. Cool completely, then cut into long narrow triangles for garnishing the milkshake. (Best if served the same day. Extras may be stored in an airtight container for up to a day or so.)

To Make the Shake

1. In a small saucepan, combine 1 cup milk and 1½ cups marshmallow fluff. Over low heat and stirring frequently, heat just until marshmallow fluff completely dissolves. Remove from heat and chill to cool.
2. Just before serving, prepare 2 tall or 4 short glasses for serving. Pour 2 tablespoons of milk into a wide shallow bowl. In another wide shallow bowl, pour ¼ cup of the Rice Krispies cereal. Dip the rim of the glass into the milk, then the cereal and allow the cereal to dry on the rim of the glasses.
3. In a blender, pour in the cooled milk and marshmallow mixture, then add the ice cream. Blend until smooth and frothy. Add ¼ cup of Rice Krispies cereal and briefly pulse again until combined.
4. Pour the milkshake mixture into the prepared glasses, and top with a prepared Rice Krispies Treat.