Beautiful cake. My guess would be great piping skills to create the 3-d sun and clouds and an airbrush for the shading.
Im not 100% sure but it could be a bct (buttercream transfer)? Maybe someone else would know fo sure but by looking at it, thats what i think it is.
It's amazing what can be done in buttercream. If you look at my photos you can see a frankenstein and a crab. They are done with buttercream. All I did was pipe the buttercream on in a general form, then I took hot water and a large paint brush. Dip the paint brush in the hot water then dry it off. And go over the butter cream to smooth it out.
The heat from the hot water will melt the butter cream and smooth it out.
Oh yea, One big tip.... make sure that your environment is not warm. My bulldog was a HUGE problem because my environment was warm and his jowels and belly dropped on me as soon as the darn thing was finished. I had to put him in the freezer for a while till he solidified and had some cold to him before I... ahem...finished him again.
Hope that helps.
I was looking at the sun cake...and if you look closely...its butter cream...the rays are what appears thick b/c piped up and over the cake, and then draped onver the 2nd tier, and the sun...is piped and shaped on that same tier and then colored, and maybe airbrushed to get the effects....thats my thoughts.
VERY NICE WORK!!! I love it...as for the clouds...I say b/c and also painted or even color icing.
hope this helps, would take work but what an effect if you can do it! Im would love to try this.
I recently googled this pic and I was in awe I wanted to make this too