Preheat the oven to 180c/350f/gas mark 4. Put 12 paper cases into a muffin tray. Blend the cocoa powder and hot water and set aside. Place the butter and aster sugar in a large bowl and beat together until light and fluffy. Gradually beat in the eggs, and then beat in the cocoa mixture. Sift the flour and using a metal spoon, fold in gently. Spoon the mixture into the paper cases. Bake in the preheated oven for 20 minutes, or until risen and firm to the touch. Transfer to a wire rack and leave to cool. To make the topping stir the nuts into the melted chocolate and spread a little of the mixture over the top of the cupcakes. Lightly stir the mini marshmallows and glace cherries into the remaining chocolate mixture and pile on top of the cupcakes. Leave to set.