I have somebody that wants this cake but instead of fondant details it would be chocolate details and the owl would be the smash cake. The rest of the cake is a 4 layer 10" cake.

AI'm not certain I understand the question. The fondant decorations would be made of modeling chocolate? The owl would be on a smash cake or would be a smash cake on top of the other cake or would be decorate (like piped) on a smash cake?

Yeah, kind of confusing.

Oops sorry, the owl is the smash cake placed on top of the other cake. The buttons and border would be molded chocolate. The letters would be poured chocolate in molds. The costumer doesn't want any fondant on the cake. So the cake would be iced in buttercream. I hope that helps clear things up.