8 ounces bittersweet chocolate, chopped up
2 T unsalted butter
3/4 cup heavy cream
2 T liqueur (Grand Marnier, Dark Rum, Kahlua, Amaretto all make lovely additions)
Set chopped chocolate in a medium-small mixing bowl. A stainless steel bowl is your best bet in case you need to reheat (I will explain that later).
Measure cream and butter into a small sauce pan and heat over medium heat, to a simmer. Be careful - if it boils it will quickly expand up and over the sides of the pot.
Quickly pour cream over chocolate and let sit for 2-3 minutes. Stir very gently (you don't want to add any air or loose too much heat) until smooth and the chocolate is all melted.*
Now it has to cool to a good spreading consistency. If you're in a hurry, you can set the bowl over ice (or stash it in the fridge or freezer) and stir frequently with a spatula to bring down the temperature. I usually just park it on the counter and check in on it every so often, tho this always takes longer than I think it will.
Ganache is done when you think it is. I like it so be the consistency of frosting.
*If the chocolate doesn't melt all the way you will need to reheat it. Bring a small pot of water to a boil and set the stainless steel bowl over the pot. The bottom of the pot should not touch the water. Turn down the flame to the lowest possible setting once the bowl is positioned, then stir gently until the chocolate is smooth and melted.