Ganache for Mud Cake

Melt 100 mls. Whipping Cream with 150gms. Dark Chocolate Buttons.
 If you use a bowl in the microwave, you should use the defrost setting (a minute at a time). Stir at each interval. Another good way of melting this mixture is in a bowl over a saucepan of water. (Heat slowly). Do not boil. A double boiler is also a good option. Mix constantly until smooth and glossy. Leave until cooled and it will thicken. To cover, leave mud cake in the tin and pour ganache over. Leave to set or place in fridge. Decorate with swirls of whipped cream.