Cream the butter and sugar together until pale in colour and fluffy in texture.
Add the vanilla extract and beat some more.
Beat in the eggs, one by one, adding a little of the flour if it curdles.
Sieve in the dry ingredients and gently stir until just combined, adding the water near the end.
Divide the mixture between 24 mini muffin moulds (cases optional).
Bake in a preheated oven at 180℃ (350℉, Gas 4) for 15 to 20 minutes, when the cakes should be well risen and firm to the touch.
Insert the chocolate centre nozzle into the cakes and inject a little of the filling into the centres.
Leave in the moulds to cool for 10 minutes or so, then turn out onto a wire rack to cool completely.
Melt the chocolate in a bowl suspended over a pan of hot, not boiling, water. Allow to cool a little.
Beat the butter and icing sugar until smooth and creamy, then beat in the whisky followed by the chocolate.
Spread onto the cooled cakes and decorate with a dark chocolate tear drop.
Can make 12 cupcakes instead of 24 mini ones, but increase the baking time by five minutes.Please note: calories and other nutritional information are per serving. They're approximate and will depend on exact ingredients used.