Whisk the eggs and sugar together in a mixing bowl until pale and frothy. Using a wooden spoon, slowly work in the flour, ground almonds or hazelnuts, baking powder, lime rind and salt.
Add the chopped pistachios and hazelnuts and knead lightly to form a soft dough. Shape the dough into a thick log, about 25 cm (10 inches) long and 10 cm (4 inches) wide, then flatten it slightly with the palm of your hand.
Transfer the dough to a greased baking sheet and bake in a preheated oven, 180°C (350°F), Gas Mark 4, for 35–40 minutes until light golden. Remove from the oven and leave to cool for 5 minutes, then cut into 5 mm (¼ inch) thick slices using a serrated knife.
Arrange the biscotti directly on a grill pan and cook under a preheated low grill for about 4 minutes on each side until crisp and golden. Transfer to a wire rack to cool.