1. Shell the shrimp and devein them. Wash them under running water, drain and pat dry with absorbent paper towels. Set aside while you make the soup.

2. Pour the water into a large saucepan and bring to a boil. Add the lime leaves and chopped lemon grass, reduce the heat and simmer for 10 minutes. Add the fish sauce and cook for a further 5 minutes.

3. Add the shrimp and lime juice to the pan and cook gently over a very low heat for a few minutes, until the shrimp become firm and turn a pale pink color.

4. Add the sliced cilantro, green onions and red chili strips to the soup. Check the seasoning, adding salt and pepper if wished, and serve very hot in a small bowls.