For the chocolate flan, whisk the cocoa powder and milk until smooth. Mix eggs with powdered sugar, cocoa milk and whipped cream in a high mixing bowl with a hand blender. Add chocolate syrup and let the mixture rest for 10 minutes. Rinse an ovenproof gratin dish with cold water and pour the chocolate mixture through a fine sieve into the dish. Cover with foil.
In the meantime, finely puree 125 g raspberries with lemon juice and powdered sugar and pass through a sieve.
Cook the chocolate flan in a bain-marie or steamer for 40 minutes at 100° C.
Serve the chocolate flan with raspberry sauce, vanilla ice cream and whipped cream.