Yes you can. First cool the ganache uncovered for at least 30 minutes on the counter (at room temperature),then for at least 2 hours (or until it reaches the desired spreading consistency) in the fridge. Stir the refrigerated ganache every now and then for even cooling. Get the ganache out of the fridge at least 20 minutes before frosting the cake. This will give it some time to soften, making it easier to spread and pipe onto the cake.