Rinse dried shiitake mushrooms under running water; Soak them in water for 15 minutes; Remove them; Fill a bowl with 250ml water; Put the dried shiitake mushrooms into the bowl of the water; Leave it for 3 hours; Remove and drain them; Set a fine-mesh sieve on the top of a mixing bowl; Pour the soaking water through the sieve for later use.
Discard any wilted soy bean sprouts; Soak them in water for 15 minutes, remove them, and rinse them under running water for 5 minutes (repeat the soaking and rinsing for 5 times); Drain them.
Rinse and drain a carrot; Trim a bit off each base; Peel it with a Y-shaped peeler; Rinse it under running water; Drain it; Cut it into chunks.
Rinse and drain water chestnuts; Cut off the top and the bottom of water chestnuts with a paring knife; Cut around the sides of each water chestnuts with the knife till all the skin is removed; Rinse them under running water.
Fill a stockpot with 1.3L water; Add all the ingredients (including 700ml dried shiitake mushroom soaking water); Bring to the boil over a high heat; Turn to a low heat; Cover the pot with its lid; Cook over a low heat for 2 hours; Stir seasonings into the soup; Turn off the heat; Arrange it in serving bowls; Ready to serve.