Preheat the oven to 180C/350F/Gas Mark 4.

Place the sweet potatoes on a tray and roast for 35–45 minutes, or until soft.

Remove from the oven and let cool enough to handle.

Meanwhile,whisk together the miso and water.

Split the sweet potatoes lengthwise and place on a parchment-lined baking sheet.

Spread some of the miso mixture on the cut side of each sweet potato, then return to the oven to roast for another 10 minutes, or until the miso topping is nicely browned.

Dress with a drizzle of olive oil, a pinch of salt and the toasted sesame seeds.