Preheat the oven to 180°C.

Prepare a loaf pan (25cm x 10cm) and line it with baking paper.

In a medium bowl, mix the dry ingredients (except for the sugar): wholemeal spelt flour, potato starch, cocoa powder, baking powder, baking soda and salt.

Grate the courgette and set it aside.

Using a stand mixer (or hand mixer), beat the whole eggs until fluffy (about 6-8 minutes). Continue mixing and add the sugar, one spoonful at a time (about 2 minutes). Continue mixing and very slowly pour the oil into your batter.

Reduce the mixer speed and add the dry ingredients, mixing just until combined. The batter will be very thick at this stage, but it will become thinner after adding the courgette (next step).

Add the grated courgette and chopped milk chocolate (optional) to the batter and mix everything with a spatula until combined.

Transfer the batter to the prepared loaf pan. Place it on the lower shelf of the oven. Bake for about 60 minutes or until a skewer inserted into the centre comes out clean.