I just Remove the shrimp shell but leave the tails (for good appearance). Then cut open the back of each shrimp to remove the veins. Also clean the mushrooms with water and dry them well before wedging each into quarters. Bring water to boil, then add lemon grass, lime leaves, and shrimps. When the shrimps turn pink, add mushrooms and salts. Remove the pot from heat after boiling. Then season with fish sauce, lime juice, and hot peppers. Serve the soup while still hot and garnish on top with pieces of coriander leaves.