Remove the outer leaves from the lemon grass. Knock the lemon grass with the back of a knife, then cut it into pieces. Wash the fish, dab dry and cut into bite-sized cubes. Peel and grate the ginger. Peel garlic and chop finely. Pour the beans into a sieve, rinse and drain
Heat the oil in a pan. Fry the fish for 2-3 minutes while turning. Fry the ginger and garlic briefly. Add coconut milk, broth, fish sauce, sugar, lemon grass, beans and chili flakes. Simmer for about 4 minutes. Mix starch with a little water. Boil the stock with it, bring to the boil again and season to taste
Wash the coriander, shake dry and chop coarsely. Arrange the fricassee in small bowls, sprinkle with coriander. Basmati rice tastes good with it