Place the almonds and the pistachio nuts into a food-processor and chop or grind them until they are very finely ground. Set aside
In a large clean bowl cream the butter and sugar together until pale, light and fluffy. Add the pistachio paste and the finely ground nuts, and mix in gently until smooth. Add the eggs one by one, beating well after each addition, then pour the batter into the prepared baking tray. Use a spoon or a spatula to smooth out the batter evenly.
Bake for 30 minutes or until golden brown and firm to the touch. It should spring back when you press it gently with your finger. Then remove the cake from the oven and allow it to cool in the tray.
When it’s cool, cut it into lovely square tiles and dust with icing sugar to serve.
This cake stays moist for a good two to three days because of the oil from the nuts.
Bryn's Tip * You can buy pistachio paste in specialist baking stores. But if you cannot find it, substitute it with an extra 20g of ground pistachio nuts.