Preheat oven to 180 degrees C. Line cupcake tins with paper patty cups (this will make 36 cupcakes, so bake in batches if necessary).
In a bowl, combine the flour, sugar, cocoa, bicarb soda and salt then mix well. Make a well in the centre.
In a separate bowl, whisk together the eggs, milk, water, oil and vanilla. Pour into the dry ingredients and mix until smooth. Fill each patty cup half full with the batter.
Bake 15-20 minutes or until a skewer inserted in the centre comes out clean. Let cool.
Meanwhile, make the cream filling: in a bowl, combine the cream, sugar and vanilla and beat until stiff peaks form. Use to fill a piping bag.
Insert the tip of the piping bag into a cupcake and push down almost to the bottom. Start filling with cream while slowly removing the tip. Repeat with all cupcakes.
Decorate the top of each cupcake with remaining cream. Serve!