1. Prepare the broth. Peel and crush the garlic. Peel and grate the fresh ginger. Put the garlic, ginger, and spices with the oil in a large saucepan. Heat for 1 minute over medium heat, stirring. Add 1.2L of water, soy sauce, and fish sauce, and bring to a boil. Reduce to medium heat and simmer for 10 minutes.
2. Cut off the roots and damaged part of the spring onion, remove the first layer of skin, and cut into thin slices. Remove the earthy part of the mushroom stems, rinse them quickly, and slice them.
3. Add the rice vermicelli and peeled shrimp to the broth, continue cooking for 2 minutes. Then add the mushrooms and spring onion, and cook for another 1 minute.
4. Serve hot with a wedge of lime and optionally garnished with chopped coriander.