Line an 8x11½ inch baking dish with parchment paper- make sure to leave enough overhang on two sides
Prepare the Chocolate Mousse according to the package. Fold in marshmallows. Pour mixture into the baking sheet and freeze until solid (2-4 hours)
Using the edges of the parchment paper, lift the frozen mousse out onto a cutting board. Slice the mousse into 18 equal squares and sandwich between two graham crackers. Return to freezer for about 15-30 minutes before dipping in chocolate or serving.
1. Fill the bottom of a double boiler or saucepan with an inch or two of water and bring the water to a simmer over medium-high heat.
2. Transfer all the chocolate into the top of the double boiler or the heatproof bowl and set this over the simmering water.