Heat peanut oil (or regular cooking oil) in a pan. Pound the fresh turmeric, shallots or small onions, black peppercorns, and chili peppers together until finely crushed, then add to the hot oil. Sauté quickly, then add the catfish and gently stir to avoid breaking the fish. Add the shrimp and stir-fry for a few minutes. Season a bit saltier than usual. Lower the heat and simmer for 5-10 minutes so the shrimp and fish absorb the flavors, then turn off the heat.

In a pot, bring about 6 1/3 cups water (1.5 liters) to a boil. Add all the cooked fish and shrimp from the pan. Gently stir to avoid breaking the fish. Continue simmering and skim off any foam to keep the broth clear. Cook for another 5-10 minutes, taste and adjust seasoning as needed, then turn off the heat.