Once the chocolate has melted into the cream, leave the ganache uncovered at room temperature. If you cover the ganache while still hot, little drops of condensation will drip from the lid and on to your ganache. Once cooled, cover your ganache with plastic wrap and make sure the wrap touches the surface of the chocolate. Leave to set at room temperature for at least 4 hours or overnight before using. This is the best consistency for spreading, filling between cake layers and piping.