I love the Betty Crocker recipe for fudge frosting! My problem? I really need a white chocolate instead of a cocoa frosting and have no idea how to substitute white chocolate for the 2tbsp cocoa the recipe calls for.
Hello Erin, and welcome to the site. We insist on a somewhat stricter structure of our questions and answers, to make them easier to find by all other people who need this information. So, I edited your title to reflect what is said in the question body. Besides, it looked like you are asking for somebody to give you a completely new recipe, which would be off topic, as we don't swap recipes here, we troubleshoot problems and discuss techniques. But your actual question, as described in the question body, is on topic, and fits the site well. Welcome!– rumtscho ♦Oct 18, 2014 at 8:50
Forgot to mention: In substitutions questions, please include the full recipe, it is important because substitutions are so hard and one has to know what other ingredients are there. I have never heard of a Betty Crocker recipe for fudge frosting, and searching for it on the Internet only shows a ready to buy product, not a recipe.– rumtscho ♦Oct 18, 2014 at 8:52
I'm afraid this is not possible at all. Dark chocolate flavor comes from aromatics in the cocoa bean, which give flavor already in low amounts. The flavor of white chocolate is very subtle, it's a combination of the aroma of the cocoa fat and the concentrated dairy solids. You cannot add it to anything as a flavoring, because practically anything else will have a stronger flavor of its own and mask the white chocolate taste.
The only way to have a cake which is covered in something which tastes like white chocolate is to make a white chocolate ganache. But then the texture will be a ganache and not a frosting. You will not be able to use your original recipe.
See this question for the correct ratio on white ganache, many people just try it like dark (that's what I did the first time too) and it ends up liquid.