What's the best way to make a smooth chocolate sauce?

Put 100 ml of cream into a saucepan and bring it to the boil. Remove it from the heat immediately and leave for 30 seconds to cool. Add 100 g of chocolate and stir well until the sauce is smooth and glossy. You could then add a flavouring such as cherry, coffee or orange brandy if you wish, and use it at once if the sauce is to be served warm. To serve the sauce cold, stir in 2–3 tablespoons of milk and leave it to cool at room temperature, stirring occasionally.