I attempted to make the infamous coconut pecan icing that goes on german chocolate cake and religiously followed the instructions to cook over medium heat for 12 minutes. The mixture of evaporated milk, sugar, butter and eggs never thickend or turned golden brown and still looked like raw eggs after 15 minutes and in desperation I turned the heat up and ended up with a curdled mess. What did I do wrong? It doesn't say to use a double boiler. On another note, is it better to use toasted coconut and pecans or stir it in as is. Please give me some tips on how to get this icing right.