Peel and devein the shrimp, reserving the heads. Crush the shrimp heads, add warm water, stir well, then strain and discard the solids. In a pot, simmer the pork bones with a pinch of salt. Once boiling, add the fish and shrimp. When the fish and shrimp are cooked, remove them from the pot. Add the chopped straw mushrooms to the broth, then season to taste.

When the broth is well seasoned, add the banh canh noodles. The broth should be slightly thick for the best flavor. Serve the noodles in bowls, topping with fish, shrimp, green onions, and black pepper.