Place 12 paper cake cases on a baking sheet. Put the pistachios and coconut in a food processor and whizz until ground. Add the brown sugar, lime rind and juice and blend to a paste. Add the eggs and egg yolks and blend until smooth.
Drop 1 heaped tablespoon of the mixture into each cake case. Bake in a preheated oven, 200°C (400°F), Gas Mark 6, for 12–15 minutes until slightly firm to the touch.
Leave the cakes to cool slightly, then dust with icing sugar and serve with coffee or tea.