I've been known to present cake in the most unlikely of situations. Cheering a gloomy friend up with cake works a treat. Treating a friend who's boyfriend has been bad, with a voodoo doll cake adds a little humour and yummy-ness to an evening of bitterness.
Trust me, you are safer with cake than you are with wine. You provide the cake and pins and your friend can do the stabbing. Don't make this cake for a 'recently-dumped-but the boyfriend was nice' friend, it won't go down well. This is for the 'he may have been cute, but he was a douche bag' kind of thing.
Start with a sheet cake. A simple sponge that you've poured into a rectangular tin (brownie pan in my case) and let cool. Then with a sharp knife, carve out your doll.Cover in frosting. I used a chocolate buttercream. Then roll out fondant and layer over the cake. Decorate how you wish!