1. Spread marshmallow Fluff over the cereal base in a single layer.
2. Sprinkle crushed graham crackers over the Fluff, pressing them slightly into the Fluff.
3. Pour melted chocolate over the graham crackers, smoothing it into an even layer with a spatula.
Roll and Chill:
1. Slice the layered sheet in half lengthwise.
2. Roll up each half starting from the long side, similar to a sushi roll.
3. Refrigerate until firm, about 1 hour.
Serve:
1. Slice into sushi roll pieces.
2. Serve with additional melted chocolate for dipping.