Pre-heat the oven to 200°C, 180°C, gas mark 6. In a medium bowl, toss the sweet potato in 1 tablespoon of oil and the Thai spice. Spread out on a baking tray and roast for 25 minutes or until tender.
While the sweet potato cooks, add the shallots, ginger, chillies and lemon grass plus 2 tablespoons of water to a mini blender or use a stick blender. Blitz until you have a paste. Heat the other tablespoon of grapeseed oil in a large sauté pan over a medium flame. Add the paste and cook for 3-4 minutes stirring often until it just starts to colour. Add the coconut milk, stirring until smooth, then add the fish sauce, juice of 1 lime and sugar along with the stock. Stir to combine, bring to the boil and then simmer for 15 minutes until slightly thickened. Once done, taste and adjust the flavour to your liking with additional lime juice, fish sauce and/or sugar.
Towards the end of the cooking time, heat the remaining oil in a wok. Once it’s nice and hot, add the broccoli and corn, and stir-fry for 1 minute. Add the mange tout and continue to stir-fry for 4 minute. Add the noodles and stir-fry for a final minute.
Arrange 4 bowls and dish the stir fried noodles and vegetables into each. Ladle over the coconut curry and then finish with the sweet potato and peanuts. Serve.