Preheat oven to 160°f or 320°f.
In a mixing bowl, or in your stand mixer, add the butter and sugar and beat for 1-2 minutes until pale and fluffy.
Add eggs in, one at a time, beating well between each addition.
With a rubber spatula, mix in the flour, baking powder, cinnamon, hazelnuts and chocolate chips.
Tip the dough out onto a lightly floured surface. Gently knead the dough to form a ball.
Cut this dough in half and roll each half out to form a log.
Transfer to flat lined baking trays, one per tray and pat down slightly.
Cook for 15-20 minutes until it has fully risen and cooked but with very little colour.
Remove from the oven and allow to cool for 15-20 minutes.
Slice each log with a sharp bread knife at a diagonal into 1-2cm slices.
Lay the slices cut slide up on the lined baking tray and return to the oven for a further 10-15 minutes until golden.