Making a hard Chocolate topping for brownies

I make a chocolate topping for my brownies my melting chocolate chips and then spreading it over the brownies. I then stick the brownies in the freezer so it hardens. Once the brownies come to room temperature the topping is not as hard as I would like and is very susceptible to melting. Is there anything I can do to make it harder and more heat resistance. I want something more like a candy bar topping and not icing. When answering keep in mind I'm not a professional pastry chef or chocoaltier. I run a small business but have no professional knowledge.
updated by @todd-kelly: 04/21/15 12:15:35PM

You are heating the chocolate too hot and taking it out of temper. Slowly melt the chocolate chips up to around 92 degrees, making sure to stir very well while melting, and spread over the *cooled* brownies. Tempered chocolate is like the candy or chocolate bars you would buy in the store, they are nice and shiny, snap when you break them and don't melt the second you touch them. Untempered chocolate is like you describe, melts quickly and is not as hard at room temperature. Good Luck!Now I think I will have to make some brownies....

If you do not temper the chocolate, it will crystalize in it's more unstable forms, and be soft, and have a poor appearance. Also do not cool chocolate in a freezer. Chocolate should be cooled more slowly so all crystals forming after temper will crystalize off the stable seed from the temper. Cool too quickly and you will develop unwanted crystals, even with a good temper. Compound coating do better if cooled quickly, not cocoa butter.