http://cakecentral.com/cake-decorating-ftopict-662070-fudge.html+filling
Check out the above thread. 
A couple days late, but here is the recipe. I found the original on epicurious then changed it a bit. It is a favorite and especially great with banana cake.
Semisweet/Dark chocolate 1#
Heavy cream 2 c
Sugar 3 Tbsp
Corn syrup 3 Tbsp
Unsalted butter, soft 1/4 c
Use best quality chocolate (I prefer Callebaut). Chop up and place in a large bowl.
Bring cream,sugar, and corn syrup to a boil; whisking until sugar is dissolved.
Pour this over the chocolate. Let sit a minute, then whisk until smooth/chocolate melted completely.
Whisk in butter until smooth.
Let sit, stirring occasionally, until it thickens. If need be, place in fridge, stirring occ, to thicken it faster.
Hope you like it!
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