Preheat oven to 180℃. Line a tray with baking paper. Combine flour, sugar, baking powder, spices, salt and hazelnuts in a bowl. Add the eggs and vanilla and mix well to form a stiff dough.
Divide the dough into 2 equal portions and shape each portion into a log. Slightly flatten each log then transfer to the prepared baking sheet, leaving some space between them. Bake in the preheated oven for about 25-30 minutes, or until they are firm and lightly golden.
Allow the baked logs to cool for 10-15 minutes. Using a sharp knife, slice the logs into 5- 10mm thick slices.
Reduce oven temperature to 160℃. Arrange the sliced biscotti on the baking sheet, cut sides down. Bake for an additional 15-20 minutes, (depending on thickness) or until they become lightly golden and crisp.
Let the Hazelnut Biscotti cool completely on the tray, and then store them in an airtight container. They can be savoured with your favourite coffee, tea, or even dipped in chocolate for an extra treat.