Preheat the oven to 200°C/180° fan. Grease a 20cm x 30cm lamington pan.
1. Process the pistachios, walnuts, castor sugar, semolina, cinnamon and ground cloves until finely chopped. Transfer to a medium bowl.
2. Brush 1 sheet of pastry with a little of the butter then top with 7 more sheets, brushing each well with butter. Fold the pastry in half and place into the pan. Sprinkle the pastry with a thin, even layer of the nut mixture. Layer another 2 sheets of pastry, brushing each with more butter. Fold the pastry in half, place in the pan and top with another layer of nut mixture. Repeat the layering process until all of the nut mixture has been used. Repeat the layering and buttering with any remaining pastry sheets and brush the final layer with butter.