Divide the dried porcini and shiitake into 10 gram portions. In a bowl, soak 10 grams of porcini and 10 grams of shiitake with 300ml warm water for 30 minutes. Drain, reserving the stock. Using a spice grinder, grind the remaining 10 grams of porcini and 10 grams of shiitake into a fine powder.
In a stockpot, add 2 liters of cold water. Add the chicken thigh, ginger, Sichuan peppercorn, black cardamom pod and one green onion. Bring to a boil, skimming off and discarding any foam. Add the reserved mushroom stock. Turn heat down to medium and simmer for 40 minutes.
Strain and discard all aromatics from the broth, keeping the chicken only. Add the porcini and shiitake mushroom powder, stirring to dissolve. Bring back to a boil, then simmer for five minutes. Season with salt to taste.
Transfer the stock base into the hotpot. Add Chinese dates, tomato slices, remaining green onion, and 100 grams each of the whole fresh enoki, beech and king oyster mushrooms. Boil again, continuing to cook for 5 minutes. Add the remaining mushrooms throughout the meal and enjoy!