Use less cream or more chocolate, sounds like yours is a pouring consistency. What is the ratio of chocolate to cream you are using?
Edited to add - if too thin, you can whip it up - comes out like chocolate mousse!
The ration for ganache is 2:1 - 2 parts chocolate to 1 part cream. Once you have thoroughly mixed the heated cream and chocolate, put saran wrap over the bowl and press it down onto the ganache. It will look like chocolate syrup. Leave over night and the next day it will be thick and creamy.
As soon as the cream has come to the boil are you then adding it to the chocolate pieces - then allowing it to cool for a minute or two - then with your paddle attatchment beating it until it is whipped?
Once this is done just transfer it into a clean bowl ( if you wish) and let it stand for at least 6 hours - over night is best/all day.
That way your Ganache will thicken to the right consistancey.
Enabling you to tort/fill with it...and even use as an outter layer coating.
Bluehue. 
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