Marshmallow Fluff Help
What about injecting the marshmallow fluff filling after the cake is baked? Will that qualify for your contest? That is how it's done with twinkies. The kitchenkrafts website has a "twinkle" pan that comes with a filling injector, but you could probably adapt a cake decorating nozzle to work the same way.

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About: I love to cook and to play golf, just not at the same time.
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Last bite on earth: Chocolate cake and a Cosmopolitan.