Heat the oil in a large, heavy-based saucepan. Add the curry paste and turmeric and cook for 1 minute, then stir in the coconut milk, stock and lemon grass and simmer for 2 minutes.
Add the baby sweetcorn and mushrooms and cook for 2 minutes, then add the noodles and sugar snap peas and cook for a further 3 minutes. Ladle into warmed serving bowls and top with the bean sprouts. Sprinkle with the coriander leaves and serve with lime wedges.