1.Preheat oven to 170°C (150°C fan-forced). Line 12-hole muffin standard pan with paper cases.
2.To make chocolate ganache; bring cream to the boil in small saucepan; remove from heat. When bubbles subside; stir in chocolate until smooth. Transfer to small bowl; refrigerate 1 hour, stirring occasionally, or until firm. Beat with electric mixer until smooth.
3.Meanwhile, stir chocolate and the water in small saucepan over low heat until smooth.
4.Beat butter, sugar and eggs in small bowl with electric mixer until light and fluffy. Stir in sifted flour and cocoa, meal and warm chocolate mixture. Drop ¼ cup of mixture into cases.
5.Bake about 25 minutes. Stand 5 minutes; turn, top-side up, onto wire rack to cool.
6.Fit a large piping bag with a large fluted tube, half-fill the bag with ganache. Pipe swirls on each cake, top with smarties and rainbow chips.