Toss the diced sweet potato in a dash of oil, and spread it out in a single layer on a baking tray. Roast at 190°C (Gas Mark 5 / 375°F) for around 30 minutes, or until soft and crispy on the edges.

A few minutes before the sweet potato is ready, begin the sauce. Heat another dash of oil in a wok or large frying pan, and add the spring onions, garlic, chopped chilli, and chopped cashew nuts. Cook over a medium-low heat for a couple of minutes, stirring regularly, until fragrant. Then add the soy sauce, sriracha, honey, peanut butter, and water, and mix well to combine. Allow to cook for another minute or so until it's thick and sticky.

Add the tomato wedges, cooked noodles, and roasted sweet potato, and mix to combine. Season to taste (you probably won't need any salt, as soy sauce is salty), and serve topped with fresh coriander (cilantro), and extra spring onions and cashew nuts if desired.