02Meanwhile, make the ganache. Melt butter in a small saucepan over medium-low heat. Add milk, sugar, cocoa powder and salt. Whisk until incorporated. Once it reaches a low boil, whisk gently for 1 minute and remove from heat. Let come to room temperature.03Twenty minutes before frosting the cake, put the ganache in the refrigerator until firm. Gently remove cake from pan. Pour the ganache over the cake, covering the top and drizzling it over the sides and in the center.