I need to decorate an ice cream. Should I use buttercream or chocolate? I want to make a chocolate stencil to decorate on the outside of my round cake but I would I get it to curve to fit the round cake?

I've never done an ice cream cake, so I don't know what to decorate it with. As far as stencils are concerned, most stencils have enough give to them to bend around the side of a cake. It's hard to stencil the sides of a cake with only two hands, though. It's generally better to have one person to hold the stencil against the cake and another to actually put the icing on.