Preheat the oven to 400°F.
In a large bowl, mix together the flour, baking powder, baking soda, mixed spice, and salt. In another bowl, cream the butter and sugar with an electric mixer. Add the eggs one at a time, mixing well after each addition, and then beat in a third of the flour mixture followed by a tablespoon of the sour cream, repeating till all is used up.
Put the water, chocolate, and instant coffee in a pan and heat gently, just until the chocolate’s melted. Fold this into the cake batter, but don’t overheat. The mixture will be very thin, but don’t worry about that: just pour carefully into the waiting muffin cups and put in the oven for about 20 minutes, until each little cake is cooked through but still dense and damp. Let cool in the pan for 5 minutes, then slip out the cakes in their papers and sit on a wire rack until completely cold.
To ice them, make up the royal icing according to the package instructions and cover the tops of the cupcakes thickly. Cut out holly leaves and sit two on each cake, and then press on your berries, perhaps putting two on some, three on others.