Andrea Boueiz's chocolate chestnut cake

Preheat the oven to 180 Celsius.Prepare a ramekin or a small mold about 10 centimeters in diameter. Line the inside with parchment paper or butter to prevent the cake from sticking when unmolding.In a small saucepan, add the chocolate and milk, and melt over very low heat.Once the chocolate is melted, remove it from the heat and add the butter. Stir until the butter is melted.Add the sugar and chestnut cream. Mix well.Add the egg and stir just to incorporate. Using a spatula, add the flour and salt without overmixing.Pour the mixture into the mold and bake for 15-20 minutes. The center should remain soft. For a large cake, bake for 20-30 minutes.Let cool for 5 minutes, unmold and transfer to a plate.Decorate with powdered sugar or cocoa nibs.Serve warm....