Preheat oven to 180C/ 160 C fan. Grease and line a loaf tin and set aside.
Grate the courgette, leaving the peel on, and spread out over a thickness of paper towel (or a clean tea towel) to drain while you prepare the batter. I use a little bit more towel on top (or a second clean tea towel) to press out any extra moisture, you don't want the courgette watery.
Using a fork, mash together the butter and sugar until well combined. I've tried using a mixer for this but I find mashing it with a fork results in a better consistency in the final bake.
Whisk in the egg and add the mashed banana.
Measure in the plain flour and bicarbonate of soda. Use a wooden spoon to mix until just combined. Don't overmix.
Fold in the grated courgette and all but one tablespoonful of the dark chocolate chunks.
Spoon into the prepared loaf tin, smoothing over the top. Sprinkle the remaining chocolate chunks over the top of the batter.
Bake in the centre of the oven for approximately 60 minutes, until the top is golden.
Leave to cool in the tin for ten minutes before transferring to a wire rack to cool completely.
Slice and eat as is, buttered, or with some chocolate hazelnut spread for an extra indulgent treat.
Mum of three, daydream adventurer, OU Life Sciences graduate, occasional crafter, ex-pat Canadian & quite possibly Britain's most northerly food blogger.