In a medium bowl, put together praline paste, chopped chocolate and butter, and melt in a microwave until everything is melted and the mixture is smooth.

Add rice crispies and stir until they are evenly coated.

Spread the coated rice crispies at the bottom of a round 24-centimeter (nine-inch) baking pan and press tightly to form a thin and relatively stable base.

Cool the base for half an hour in the freezer.

In a small bowl, mix gelatin and water and leave for about 10 minutes at room temperature until gelatin absorbs all the liquid.

Chop the chocolate, put in a bowl and melt in a microwave or double boiler until it is completely melted. Set aside.

Place milk, instant coffee and salt in a small pot and bring to a boil.

At the same time, whisk together egg yolks and sugar into a smooth mixture.

Temper the eggs: Pour one third of the hot milk mixture into the yolks while vigorously beating, until a smooth mixture is obtained. Return the egg yolk mixture to the pot and stir well.

Continue to cook the mixture on a low-medium flame, stirring with a spatula, until it slightly thickens and reaches a temperature of 180 degrees Fahrenheit (82 degrees Celsius).

Melt the gelatin in a microwave until it liquifies and add to the pot. Mix well.

Strain the mixture and add to the melted chocolate. Mix well until you get a smooth chocolaty mixture. Cool for about 15 minutes at room temperature.

In a mixer bowl, whip the cream until firm but soft. Fold the whipped cream into the chocolate mixture until you get a smooth mousse.

Pour the mousse mixture over the base and smooth out the top. Cool the cake in the freezer for at least five to six hours, preferably overnight.

Remove the frozen cake from the baking pan and decorate with grated chocolate.

Defrost for several hours in the refrigerator before serving.