Rinse the mushrooms, put them in a small saucepan and cover with water. Bring them to a boil on high heat and swish the mushrooms to remove excess dirt. Discard the water. Rinse. Once again, cover the mushrooms and bring them to a boil, covered. Let sit 1 hour. Then drain, remove tough stems, squeeze out excess water and slice or cut in half. Bring the stock to a boil in a large saucepan on high heat, add the ginger and lime slices and cook for 2-3 minutes. Lower the heat and add the lime and lemon juice, soy sauce and chilies. Simmer for 5 minutes. Add tofu and mushrooms and simmer 5 more minutes. Taste to check the balance of hot, sour and salt -- none should overwhelm the other -- and add more chilies, lime juice or soya sauce as needed.
Serve garnished with chopped cilantro. Have a side dish of extra sliced chilies for those who like it hot. Keeps a few days refrigerated but it is best served fresh.