Super easy to make: Stuff ready-made chocolate mouse into containers which you first cover with cling-film. Put the containers in the freezer for at least 3 hours. Melt white chocolate au-bain-marie or in the microwave, spread out evenly (2mm) on a baking sheet and wait for it to dry. Take the containers out of the freezer and shortly hold them in hot water, so the chocolate mouse releases easily. Add some cacao powder and break some pieces of the white chocolate. Looks as if you have been in the kitchen for hours.
Images via: Allerhande