http://www.cakecentral.com/cake-decorating-ftopict-35474.html
Here is a link to a thread - I had the same question a while back. HTH!
Are you looking for the extended cake recipe? The one I have is:
Cake mix according to directions
1 egg
1 C flour
8 oz. sour cream or yogurt
1/3 t. salt
1 C sugar
1 t. vanilla
I don't know if this is what you need but is what I use when I make character cakes to make them deeper and to make them show up better.
Diane
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