Preheat the oven to 160°c (140°c fan oven)
Use a pestle and mortar (or rolling pin) to grind the coffee granules to a reasonably fine powder. Put to one side.
Cream the margarine and sugar together until pale and fluffy.
Add ⅓ of the egg and a spoon of flour and mix in. Continue adding the egg and flour until it is all mixed in.
Add the remaining cupcake ingredients (coffee powder, salt and milk) and mix in.
Place cupcake cases into a cupcake tin. Then spoon the mixture into the cases, the cases should be ⅔ full.
Bake in the oven for 20 mins. Check the cakes are cooked through with a cake tester (or cocktail stick).
Place the cakes on a rack to cool down. Do not ice the cakes when warm! The icing will melt.