Prepare the fondant: Melt the chocolate in a bain-marie. Add the butter and let it sit for another minute, then stir until smooth.
Split the vanilla pod lengthwise. Place it in a saucepan with the cocoa and 30 cl milk. Bring to a boil while stirring. In a separate saucepan, whisk the 3 egg yolks with 50 g caster sugar. Gradually pour in the hot milk mixture, whisking constantly. Cook over low heat, stirring until it thickens enough to coat the spatula. Remove from heat, cool, and discard the vanilla pod.
Combine the chocolate-butter mixture with the cooled custard, whisking vigorously. Let the cream cool, then pour into a 1-liter springform mold. Smooth the top with a spatula and refrigerate for 24 hours.
Prepare the anise sauce: Pour 50 cl milk into a saucepan. Add the lightly crushed star anise and bring to a boil. In another saucepan, whisk the 5 whole eggs with 100 g caster sugar. Gradually add the boiling milk, whisking constantly. Cook over low heat, stirring until it coats the spatula—never let it boil. Remove from heat, cool while whisking occasionally, strain, and refrigerate.
To serve, unmold the fondant by briefly dipping the mold base in hot water. Place on a serving dish and pour the anise sauce around it or serve in a sauceboat.
