Made this double barrel cake with Sharon Wee from Australia back in April 2012. She made it so easy in class :).
Firstly, there must strong internal support for the cake.
Then you ganache 2 x 8in round cake until the sides are clean and smooth and you get sharp edges on top.
Next, wrap fondant around the cake and smoothen the joints. Decorate the top tier 6 inch cake like what you would normally do. And stack it on top of the 8inch barrell.
Here’s the finish cake made in class.
Made another double barrell cake for an Arsenal fan. Arsenal logo is manually cut out in gumpaste.