Here's the situation: We have a wedding cake to do that is 3 layers per tier. The bride wants a chocolate mousse filling between the layers. The cake will be covered with a thin layers of butter cream and then fondant. The wedding is on Saturday evening, we want to assemble the tiers on Thursday. The filling needs to hold up and not separate during this period. I have found some recipes that have butter in the recipe that stay firm especially when placed in the fridge. Are there any tried a true recipes out there??