Preheat the oven to Gas Mark 4 (350F degrees). Grease a 9x5 inch loaf tin with non-stick spray and set aside.

In a large bowl, whisk together the two flours, cacao powder, bicarb, salt and espresso powder until evenly mixed. Stir in the chocolate chips and chopped hazelnuts.

In a medium bowl, whisk together the egg and the two sugars until combined. Whisk in the buttermilk, oil and vanilla. Gently stir the wet ingredients into the dry ingredients until there are no pockets of flour left. I prefer to use a silicone spatula to scrape around the bowl and gently fold the ingredients together without over-mixing them.

Pour the batter (it should be fairly thick and almost puffy looking) into the prepared loaf tin. Bake for 25 minutes then cover with foil and continue baking for another 25 minutes or until a toothpick inserted into the centre of the bread comes out cleanly.

Cool completely in the tin on a wire rack before slicing.

The bread freezes well - up to 2 months. I usually cut into slices before freezing, so I can defrost a slice (or two!) at a time. Otherwise keep at room temperature in an airtight container for 3 - 5 days.