For the tartlets, crumble the chocolate. Allow to melt in a water bath. Whip the cream until stiff, add the creme de cacao and stir into the chocolate. Refrigerate. Spread the sponge cake in a baking dish and spread the chocolate cream evenly in it. Freeze for 30 minutes.
For the mousse, whip the yolks with champagne, sugar, Marc, lemon zest and vanilla in a water bath until creamy. Soak the gelatine for 5 minutes, squeeze it out and let it melt in the hot cream. Place baking bowl on iced water, continue beating until cream has cooled. Whip the cream until stiff, mix gently.
Fill ramekins with mousse. Cool for 2 hours.
For the cassis sorbet, crush the berries, press through a sieve. Soak gelatine in cold water for 5 minutes. Boil sugar with cassis liqueur and vanilla. Add gelatine. Cool and fold in berry puree. Pour sorbet mixture 1/2 cm thick onto a baking sheet and place in freezer to set.
For the praline sauce, heat the whipped cream and let the pralines melt in it. Add the yolks. Whip until a light creamy consistency is obtained. Cool down.
Pour praline sauce onto plates for serving. Carefully remove the tartlets from the mold and turn them out onto the plates. Place a bob on top of each. Scrape off the sorbet (as a ball) and place on top. Garnish with chocolate flakes.
Tip: Do you prefer milk chocolate or dark chocolate? Depending, use whichever tastes better to you.