1. Combine the chocolate, cream and milk in a small non-stick pan over a low heat for 4-5 minutes until melted, then whisk until smooth.
2. Next, put the chestnut purée in a food processor and blend until smooth. Pour in the warm chocolate mixture, then add the egg, golden syrup, coffee liqueur or brandy and process again. Scrape down the sides. Add the amaretti biscuits and pulse once, just enough to combine.
3. Divide the mixture between 6 small pots, cover and chill in the fridge until firmed up, for about 3-4 hours.
4. In a small bowl mash the chestnut purée with the back of a teaspoon until fairly smooth, then stir in the golden syrup. Lightly whip the cream until soft peaks form and marble in the chestnut mixture. Divide between the chocolate pots, arrange the marrons glacées on top, then drizzle over a little golden syrup and serve.