I am making a cake for a 16 year old boy. I bought the Wilton helmet pan (flat) but didn't think it would be enough cake for everyone. So I am going to make a one layer half sheet cake to put under it. (I'm going to cover it with green and white fondant so it looks like a field.) I've never done the whole "add stuff to a cake mix" thing, but I'm afraid if I just use a regular cake mix, the thing will cave in. So, I'm looking for two recipes, yellow and chocolate, that I are "add to cake mix" recipes that are sturdy for baking and heavy decorating. Also looking for a tasty icing recipe. My buttercream is always gross!! Should I use a ganache under the fondant? ) Thanks for your help! )