In a medium sized pot over a high heat, heat the oil and add the red pepper, ginger, garlic, lemongrass. Cook for 1 minute.
Stir in the paste and give it a good mix.
Pour in the stock and coconut milk and bring to a simmer (Don't let it boil). Turn the heat down to medium/low.
Add the sugar and the chicken and remove the lemon grass. Turn the heat right down and cover the pan. Cook for 10 - 15 minutes or until the chicken is cooked through.
Divide between 4 - 6 bowls and top with spring onions, coriander and lime juice.