First add the sugar to the room-warm butter and beat until fluffy. Then add both eggs, one at a time. Mix the baking powder, cocoa and flour and add to the butter mixture. Next, gently mix the pistachios into the batter. Everything should only be loosely mixed, do not stir too long.

If you are using paper cups, place them in 6 solid muffin tins. Then fill the paper cups two thirds full with the batter.

Bake the cupcakes for 20 minutes. They are perfect if the tip of the knife stays clean when you test them. Leave them to cool on a rack.

In the meantime, mix the icing. First cream the room-warm butter with a mixer and then slowly add the icing sugar and pistachio paste. Add as much green food colouring as needed until the frosting is a strong green.

Use a piping bag with a decorating nozzle to decorate the cupcakes with the frosting.