Preheat the oven to 350F. Line standard muffin tins with paper liners.

Sift the cornstarch and cocoa powder into a medium bowl and set aside until use.

Add the butter and chopped dark chocolate into a large bowl and melt them in warm water (50C).

In a medium bowl, whisk together the eggs and sugar until smooth. Add the egg mixture to the chocolate mixture and stir until well mixed. Add the dry mixture to the chocolate mixture until smooth. Strain the mixture and divide it among the muffin cups.

Place a cookie sheet on the middle oven rack. Set the muffin pan on the cookie sheet. Fill the cookie sheet with boiling water.

Bake until the dough doesn't attach to your finger when touched, about 40 minutes (be careful not to bake too much). Let cool completely. Remove the cakes with their liners and freeze them until use.

Decorate the cakes with chocolate, fruits, cream, etc... Store them at room temperature for 1 hour or in your fridge for 3 hours before serving.

More Details at
http://www.chez-k.org/english/petit-cakes/chocolate-terrine/