Baking help: Allergy edition

[Anna Phor]

I'm decorating a birthday cake for a party for a child who has severe food allergies. My usual MO for kids' cakes is buttercream covered with marshmallow fondant. The marshmallow fondant is fine -- the buttercream, not so much.

I'm looking for a functional equivalent (the point of the buttercream is to float the fondant on the cake, more or less) that's dairy and nut free. Coconut is okay; soy is okay; tree nuts, peanuts and any dairy is out. Eggs are fine, too. I've seen a number of online recipes that *might* work but would like some more expert/tried-and-true advice, if anyone has it.

So far my best solutions are either a coconut-oil based frosting else one made with a soy-based margarine. I think the former would probably taste better but I'm worried about the melting point of the coconut oil being too low.

[weezy]

How about an avocado buttercream?  http://www.foodnetwork.com/recipes/alton-brown/avocado-buttercream-frosting-recipe.html

[ktmoomau]

this thing on Food 52 might help, it's for coconut whipped cream:  https://food52.com/recipes/24762-coconut-whipped-cream

I also recently made a the penuche frosting https://food52.com/recipes/20123-banana-cake-with-penuche-frosting  with carton coconut milk (if you used canned it might be better), it didn't thicken up quite as much as when I made it with lactose free milk, but I don't know if maybe didn't give it enough time to cool down as I was in a real hurry, or didn't use enough powdered sugar.  I think it would definitely work. Mine wasn't the best looking icing ever, if I had to do it again, I would try using coconut milk from a can which is a bit thicker.  But again, I was in a REAL hurry and it could have worked potentially if I had been a little better about the whole thing.

[thistle]

How about an avocado buttercream? http://www.foodnetwork.com/recipes/alton-brown/avocado-buttercream-frosting-recipe.html

This sounds good, I made a avocado/ cocoa pudding that was delicious, here's a frosting-http://paleospirit.com/2013/avocado-chocolate-frosting-paleo-and-vegan/

You might have to omit the chocolate chips, doubt they would be dairy free.

[zoramargolis]

This sounds good, I made a avocado/ cocoa pudding that was delicious, here's a frosting-http://paleospirit.com/2013/avocado-chocolate-frosting-paleo-and-vegan/

You might have to omit the chocolate chips, doubt they would be dairy free.

Here's a link to my recipe for avocado chocolate mousse on Food52. If you use a little bit less coconut milk, it will be a quite stiff ganache and would work fine as a cake frosting. If you are using bittersweet chocolate (ie. 65% or more), there won't be any milk in it. The only drawback is that the chocolate might be a bit intense for kids. If you can cut it with marshmallow fluff, it'd probably be more child-friendly.

[Anna Phor]

Thanks to all for the suggestions. The avocado ones sound interesting, but also, uh, a little challenging for my target audience (plus one of the birthday kids doesn't like avocado at all).

I ended up going the simple route; subbing earth balance margarine for the butter. Worked fine. Didn't taste as great as the buttercream but was drowned out by all the sugar, anyway.

[goodeats]

Read this late, but I just purchased Johnny Iuzzini's new cookbook, Sugar Rush. In it, he stated he used a swiss meringue as a form of frosting.