Preheat the oven to 180°C fan/200°C/ gas 6.Mix the potatoes in a roasting tin with the oil and salt, then transfer to the oven and cook for 40 minutes.Meanwhile, mix together all the ingredients for the dressing. Depending on your brand of peanut butter, you may need to add a little more coconut milk so you have a thick, spoonable dressing consistency. Taste and adjust the seasoning as needed.Once the potatoes have had 40 minutes, add the green beans and beansprouts. Add a splash more oil if needed, then return to the oven for a further 20 minutes.Sprinkle the potatoes and vegetables with the coriander and serve warm or at room temperature, with the dressing alongsideNote: Check the seasoning of the dressing by putting a little bit on a cooked potato, and tasting. Add more soy sauce to the rest of the dressing as needed.