This recipe is for sandwiching and covering cakes. Because of its high chocolate content, it can safely be left at room temperature for a few days. Right after it is freshly mixed it is thin enough to pour on cakes for coating. After a few hours of resting, it will set in a perfect consistency for sandwiching, covering, piping and decorating cakes. If refrigerated, ganache will be hard like butter, and can be rolled into  truffles. A cake that has been covered with ganache , then refrigerated till hard, is ready for covering with rolling fondant.

Ingredients: 

1 1/2 pints  heavy whipping cream (usually sold in pints or quarts)
36 oz of dark chocolate, cut into small pieces (an OK and easy substitute is
semi-sweet mini chocolate chips).
7 oz butter (2 sticks minus 2 T) cut into small pieces, at room temperature.

Method:

Put chocolate  in a large bowl.
Bring the cream to a boil, removing from heat after it has boiled for a few seconds.
Pour cream onto the chocolate  and whisk till melted.
Add butter pieces and mix till melted.
Cover and let sit at room temperature.