Step 1

Combine the hot pepper flakes, sesame oil, and black pepper in a small bowl. Mix well with a spoon until the hot pepper flakes absorb all the oil. Set aside.

Step 2

Heat the vegetable oil in a large saucepan over medium-high heat. Add the onion, garlic, the chopped white part of the green onion, and mushroom. Stir with a wooden spoon until the onion and garlic are slightly brown and crispy, 2 to 3 minutes. Add the stock. Cover and cook for 5 to 6 minutes, until it's boiling vigorously.

Step 3

Add shrimp, oysters, and mussels. Cut the tubes of tofu in half and squeeze them into the boiling stew, and then break up the tofu a bit with a wooden spoon. If using silken tofu, scoop or squeeze from the box into the stew.

Step 4

Add the fish sauce (or salt to your taste), half of the hot pepper mixture, and stir a few times.

Step 5

Cover and cook for 5 to 6 minutes, until the seafood is fully cooked and the broth is infused with its savory flavor.