Pre heat the oven to 180C/ fan 160C/ gas 4. Line a baking sheet with baking parchment.

In a large bowl, mix the flour, sugar and baking powder. Stir in the eggs then use your hands to bring the mixture together. Add the chocolate chips, almonds, vanilla, cinnamon and zest and gently knead for a minute to form a firm dough.

Tip out the dough onto a lightly floured work surface. Divide the dough in half and form each piece into a log shape, about 20cm long and 5 cm wide. 
Place on the baking tray and bake for 25 minutes. Remove from the oven (the dough will still look pale at this point). Reduce the oven temperate to 160C/ fan 140C.

Cool for 10 minutes on the tray then transfer to a chopping board and slice the logs, diagonally, into 2cm thick slices.

Return the biscotti to the baking tray, cut side down, and bake for 15 minutes. Turn the tray over and bake for a further 15 minutes until dry all the through to the centre.

Remove from the oven and place on a wire rack to cool.

Melt the dark chocolate in the microwave. Dip half the biscotti into the melted chocolate and sprinkle over the almonds and zest. Set aside to cool before eating.