Preheat your oven to 180°C (160°C fan). Line a baking tray with parchment paper. You should hear the fan kick in softly as the oven reaches temperature — this ensures even heat distribution.

Mash the bananas in a large bowl until they form a smooth, almost liquid paste with only a few tiny lumps remaining. The colour should be a pale golden yellow, and the smell will be intensely fruity and sweet.

Cream the butter and brown sugar together in a separate bowl using a stand mixer or hand mixer until pale and fluffy, about 3 minutes. The mixture should look aerated and feel light when you lift the beaters — it will smell like caramelised sugar.

Beat in the egg and vanilla paste until fully combined. The batter will become glossy and smooth, with a rich, fragrant aroma. Scrape down the sides of the bowl with a spatula to ensure everything is incorporated.

Fold in the mashed bananas gently with a rubber spatula. The mixture will look slightly curdled at this stage — this is normal. The texture should be soft and creamy, with a pale tan colour.

In a separate bowl, whisk together the plain flour, rolled oats, bicarbonate of soda, salt, and cinnamon. The oats will look like tiny flakes among the flour. Tip the dry ingredients into the wet mixture and fold until just combined — stop when you can no longer see streaks of flour. The dough will be soft, sticky, and smell warmly of cinnamon and banana.

Fold in the dark chocolate chips if using, distributing them evenly. You should see small dark flecks throughout the pale dough.

Chill the dough for 15 minutes in the refrigerator. This prevents the cookies from spreading too much during baking. The dough will feel firmer and less sticky to the touch when you remove it.

Scoop heaped tablespoons of dough onto the prepared baking tray, leaving at least 5cm of space between each cookie. Roll each portion into a rough ball — the surface should look slightly craggy, not perfectly smooth. Press a few extra chocolate chips onto the tops for visual appeal.

Bake for 12 minutes until the edges are set and golden brown, but the centres still look slightly soft and pale. The cookies will puff up and the kitchen will fill with a toasty, sweet aroma. Remove from the oven and immediately sprinkle with a pinch of flaky sea salt. Let them rest on the tray for 5 minutes before transferring to a wire cooling rack. The cookies will continue to set as they cool, and the centres will become soft and tender.