Share '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…