Gently heat the chocolate and butter together in a pan (or use a Bain Marie if you prefer).
When the ingredients have almost melted, remove from the heat, stir, and add the milk or coffee. Leave until mixture cools a little.
In a bowl, beat the eggs and sugar together.
Stir in the chocolate mixture.
Combine the flour and cocoa, then add to the other ingredients. Stir until well mixed.
Pour into the cupcake cases (it's a fairly thin batter) until they are about half way full.
Bake for 12-14 minutes. The top should be fairly spongy when pressed.
Remove from the oven and set to one side while you make the topping.