I have been experimenting lately with homemade chocolates and I was wondering about different fillings. I have a block of Merckens Caramel. Can I melt that down with perhaps some cream or condensed milk and use that for filling? Can I just use a thickened ganache? I see many recipes in this catagory call for the addition of "invert sugar". What purpose does that serve? And finally, what is the shelf life/storage of this kind of candy? I apologize for all the questions, but I've been unable to find the answers anywhere. Thanks in advance for any input!