Add the sugar to a pan and turn the heat to high to make caramel for the braised fish. Meanwhile, peel and halve the onion, then slice it lengthwise and crosswise into small pieces. Rinse the catfish pieces briefly under running water.

When the sugar melts and turns a deep amber color, add the water, olive oil, soy sauce, fish sauce, and half of the chopped onion. Stir well. Place the catfish pieces in the pan. Reduce to medium heat.

Here are all the vegetables for the dish. First, bring about 4 1/4 cups (1 L) of water to a boil in another pot, add the salt, and turn the heat to high to prepare for boiling the vegetables. If you have pork broth with 1/2 teaspoon salt already added, you can use that instead. While waiting for the water to boil, peel the daikon radish and wash the Korean squash. Cut them into bite-sized pieces. Once the water boils, add both vegetables to the pot and boil for about 10 minutes.

Next, peel the chayote, wash, halve, and cut into small pieces. When the daikon and squash are tender, remove them from the pot and add the chayote. Cover and boil until tender, about 10 minutes.

While the chayote is boiling, trim the ends and remove the strings from the Japanese green beans, then wash them. When the chayote is tender, remove it from the pot and add the green beans. Boil for 4-5 minutes. Meanwhile, wash and chop the napa cabbage. Now is a good time to check if the fish is fully cooked, then turn off the heat.

When the green beans are tender, remove them from the pot and add the napa cabbage. Boil for 4-5 minutes. When the cabbage is tender, remove it. Add the remaining half onion to the leftover vegetable broth in the pot, bring to a boil for 1 more minute, then turn off the heat. Now you have a hot, nutritious soup to enjoy!