I am making a cake for a little boy that has never had an actual decorated cake. He is turning 3.  He usually only gets cupcake with chocolate frosting. He cannot have eggs, soy or dairy. I need a good "vegan" white buttercream recipe that taste good. Even a good cake recipe if you have tried it and it is amazing. I want this to be the best experience for him. Please help.

I wonder if you couldn't just sub the butter for coconut milk? The kind that is full fat and has the cream on the top.....mmm I love the cream part.  I've been meaning to try that since I have a large jar of it. For the 'milk' part, you could just use water or coconut milk. I read some other threads, and they said they use coconut milk to sub for the milk part, not sure about the butter part though.

I don't know if this is what you're looking for, but I found this recipe linked on another thread: http://cakecentral.com/b/recipe/Hawaiian-Haupia-Coconut-Filling

almond milk?

In the UK we have a product called Pure - they do a soy margarine and a sunflower one and both are vegan. I have used the sunflower one, literally 1 part margarine: 2 parts icing sugar with a bit of vanilla to taste and it worked great and tasted like any other basic butter cream. I find with 'free from' stuff simpler is better, once things get complicated, things go wrong. I can heartily recommend 'Vegan cupcakes take over the world' by Isa Chandra for cupcake recipes (I don't know how well they can adapt to being full sized cakes) and I'm yet to have a frosting from that book fail. There are a few recipes in it where the soy products would not be able to be substituted for other things, but there are a fair number where the soy product could be subbed for an alternative (say coconut or oat milk) and there are a fair few that have no soy in at all.