Soup greens clean or peel, wash and roughly dice. Peel onions and garlic, cut into large pieces. Heat the oil in a large pot. Fry the onions, garlic and soup greens for about 5 minutes until light brown, turning them over
Wash the chicken breast and place it on the soup vegetables. Add 1 1/2 litres of cold water, bay leaf, 1 teaspoon salt and peppercorns (meat should be covered). Bring to the boil and simmer at low heat for about 1 hour. Remove any foam that develops in between with a skimmer
Remove the meat from the stock and let it cool down. Peel and finely chop the ginger. Clean and trim mushrooms. Brush and wash pumpkin thoroughly. Cut pumpkin into slices and scrape out seeds. Cut pumpkin slices into small cubes. Wash lime leaves, dab dry. Remove the outer leaves of the lemon grass. Wash the lemon grass, dab dry, halve it if necessary and pound it with the back of a knife
Pour the stock through a fine sieve, measure out 1 litre, heat up. Add coconut milk, lemon grass, mushrooms, pumpkin, ginger and lime leaves, cover and simmer for about 10 minutes. Wash the tomatoes, drain. Clean and wash spring onions and cut into rings. Remove flesh from skin and bones, dice. Wash the coriander, shake dry and, except for something to garnish, pluck leaves from the stems and chop. 2-3 minutes before the end of the cooking time, add tomatoes, spring onions, lime juice and chopped coriander to the soup. Season soup with fish sauce, arrange and garnish with remaining coriander