I have done 2 cakes like this now...
I bought acetate sheets and cut it into strips, the height of the cake, melted the chocolate in the microwave and poured it onto the acetate.
Used a pizza cutter to cut into strips, then when set, you can just peel the acetate off the back of the chocolate strips.
thanks for the help! Where can you purchase acetate? Also, how did they make the chocolate curls around the cake?
I bought my acetate sheets at a arts and crafts store, they were quite cheap.
I did some for my son's wedding cake by using a cheese slicer and just pulling it across the slab of baking chocolate.
And, yes, I just put the chocolate strips onto the buttercream while it was still moist, then put the ribbon around to hold in place.
Hope all this info helps you somewhat??