In a saucepan, combine the condensed milk, milk, and the still-cold cornstarch, stirring carefully until completely dissolved.

Place this mixture over medium heat, stirring continuously, as it transforms into a silky, smooth cream.

Melt the semi-dark chocolate, and gently fold half of it into the hot cream, stirring until homogeneous.

In a refractor, alternate layers of maisena cookies and the rich chocolate cream.

Mix the remaining melted chocolate with the custard to make a ganache, and spread it over the dessert.

Allow to cool in the refrigerator for about 4 hours until firm.

Garnish with chocolate shavings or cocoa powder, and serve cold.