Combine all of the ingredients in a small bowl. Mix until combined and the texture is similar to wet sand. Set aside until ready to assemble.
Chocolate Mousse
Add egg yolks to a stand mixer with the whisk attachment. On the highest speed whisk yolks until they thicken and turn white in color. This takes about 3-4 minutes.
Meanwhile, heat 1/2 cup heavy cream in a medium saucepan. Do not boil just warm up the cream.
Add a splash of the warm cream to the egg mixture and stir gently. We are shocking the eggs so they do not get too hot and scramble.
Next add the egg mixture with the rest of the cream into the sauce pan.
Cook mixture until thick, 2 minutes.
Add in chocolate and stir until melted and take off of the heat.
Meanwhile, add the remaining 1/2 cup of heavy cream to the stand mixer with the whisk attachment. Whisk until cream forms soft peaks. Very carefully fold the whipped heavy cream into the chocolate mixture. Place in the refrigerator until ready to assemble S'mores Mousse.
Marshmallow whipped cream
Add heavy cream to a stand mixer with the whisk attachment. Whisk until cream forms soft peaks.
Add in sugar and vanilla whisk to combine.
Fold in marshmallows by hand.
Place in the refrigerator until ready to use.
To assemble:
Layer about 1-2 tablespoons (depending on the container you are using) of graham cracker crust in the bottom of your glass or ramekin. Press down.
Divide mousse evenly in each container. Refrigerate for at least two hours to let the mousse set.
When ready to serve top with Marshmallow whipped cream and serve immediately.