This is a rich non-greasy frosting that goes on hot and stiffens as it cools.
- Melt the chocolate and margarine together in a double-boiler or, carefully, in a saucepan on low heat.
- Mix in the vanilla extract and corn syrup, keeping the mixture somewhat hot.
- Mix in the sugar, still keeping the mixture somewhat hot. You might not use exactly 5 cups. Just keep adding sugar until the frosting is as thick as desired.
- While still hot, spread the mixture on cake or brownies.
- Mixture will stiffen.
Steaming hot cake will release moisture which may collect under a frosting. Cold cake may cause a frosting to stiffen prematurely. Thus, you should use a warm cake.
A very small amount of milk may be added if the mixture is unspreadable even while hot. Don't add more than you truly need.