Combine all the ingredients of the crust, except water, in a food processor or blender, until everything clumps together. If the mixture seems too dry, add water, 1 Tbsp at a time, till it all comes together. It will be a sticky mixture. Pat into the base of a 8" by 4" tart pan or a 6" round tart pan with a removable base. Put it in the freezer for 30 minutes.
For the filling:
In the same food processor or blender (no need to wash it out) combine all ingredients for the filling. Taste and adjust for sweetness. Pour over the chilled crust and pop it back in the freezer about 2-3 hours until completely set.
For the topping:
Combine the chocolate and coconut milk over very low heat, preferably over a double boiler, stirring continuously until smooth and homogenized. Cool, pour over the frozen filling and freeze overnight. Drizzle with some melted chocolate if you wish.
Release the completely frozen dessert from the pan. Let it thaw for about 5 minutes, cut into slices and enjoy!!