Add the graham cracker, butter and sugar to a medium bowl. Mix until the texture is similar to wet sand. Divide the crust between the tarts or use 1 regular pie pan instead. Press the crust down firmly and refrigerate for 1-2 hours to set. If you want to bake the crust place it in a 375 degree oven for 5-6 minutes or until golden brown.
To assemble the filling add heavy cream to a stand mixer with the whisk attachment. Whip until cream forms soft peaks. Take out of the bowl and set aside.
In the same bowl add the mascarpone cheese, sugar and vanilla to the stand mixer with the whisk attachment. Whisk until smooth and lump free.
Fold in the whipped cream by hand into the mascarpone cheese mixture.
Place it back on the stand mixer and whisk until combined and lump free.
Carefully spoon the filling into the tarts. Place in the refrigerator for 1-2 hours to set.