best white icing/frosting (not fondant)

[KiteyDelighty]

I have made and frozen the layers for a rainbow cake. I would like to fill and cover with a very white icing fronting(not fondant) and I was wondering if standard buttercream might be a bit sickly since there are so many cake layers. Any ideas? I am reasonably proficient and the cake will be coated the morning of the party.

Italian meringue buttercream isn't as sweet?

Seven minute icing - is the most wonderful icing ever

White chocolate ganache?

The icing used on Rachel Allens red velvet cake.... A bit of effort but devine! I think it may be a form of meranigue

Thanks for the suggestions...will check them out

How about a cream cheese icing - that should turn out white in colour and is less sweet than buttercream?

I would go for italian butter cream. Very very very white.

I also colour my icing for inside the cake one to match each tier of the ranbow so when you cut the cake it doesn´t have red, white, yellow etc. BUT I am complusive that way!