1. Bring the stock to a boil over medium heat.
2. Add the ginger, garlic, fish sauce, lemon grass, green onions, mushrooms.
3. Simmer for 2 minutes.
4. Add the shrimps and reheat into boiling.
5. Cook until the shrimps are pink, opaque and firm but no longer than 1 minute.
6. When the shrimps are cooked, pour the lime juice, chilli paste in a serving bowl.
7. Pour the soup into the bowl, stir and garnish with coriander leaves.