Peel the apples and remove the cores. Cut the apples into small pieces.
Place the apple pieces in a pot and cover them with water. Boil the apples for about 20 minutes until they are soft enough to be easily sliced with a knife.
While the apples are boiling, melt the dark chocolate chips using a double boiler or microwave. Stir occasionally until the chocolate is completely smooth and melted.
Once the apples are cooked, drain the water and transfer them to a blender or food processor with the melted chocolate and blend the mixture until it is smooth and well combined. The consistency should be similar to a mousse.
Line a baking tray or baking tin with baking paper to prevent sticking. Pour the mixture into the tray, ensuring it is spread evenly.
Refrigerate the cake for at least 3 hours or overnight to allow it to set. The longer it chills, the firmer and creamier it will become.
When ready to serve, remove the cake from the refrigerator and cut it into slices. This cake has a mousse-like texture, so it may require some extra care while handling.