If you are in a hurry for the ganache to cool, take it to the refrigerator but stir every 10 minutes with the fouet sunk in the bowl making circular movements so as not to incorporate air. In this way, ganache does not just harden at the edges of the bowl.
If you are not in a hurry, do as I do, leave it to cool to room temperature. So you don’t have to do anything until it thickens completely.
Photos: Franciele C. Oliveira