In a large pot (I use a donabe), soak 1 piece kombu (dried kelp) in 4 cups water and set it aside. To extract more flavor, you can do this step several hours in advance (up to overnight; but keep it cool or store it in the refrigerator if you live in a hot environment).
To Prepare the Hot Pot Ingredients
Check to see if there are any bones left in the 2 skin-on salmon fillets. Remove if you find them (I use fish bone tweezers). Cut the fillets into 2-inch (5-cm) pieces and ½-inch thickness.
Season both sides of the salmon with ¼ tsp Diamond Crystal kosher salt. Keep it refrigerated while you prepare other ingredients.
Peel 2 Yukon gold potatoes and cut them into quarters. Then soak them in water to remove starch.
Cut ½ lb daikon radish in quarters lengthwise, and then cut them into ⅜-inch (1-cm) slices.
Cut ½ onion into wedges and set aside.
Cut 1 ear sweet corn into 4 pieces and set aside.
Cut½ head green cabbage in half (so now it‘s ¼ of the whole cabbage) and discard the core by slicing it off. Then cut the cabbage into 2-inch (5-cm) pieces and set aside.
With a vegetable peeler, remove the outer skin of 1 carrot. Then using the same peeler, continue to peel the carrot. Alternatively, you can slice the carrot into ½-inch (1.3-cm) thickness. Set aside.
Discard the bottom ends of 1 bunch shungiku (chrysanthemum greens). Cut them into 2-inch (5-cm) pieces and set them aside.
Cut 1 Tokyo negi (naga negi; long green onion) diagonally into ½-inch (1.3-cm) thickness. Cut 1 medium-firm tofu (momen dofu) into bite-size pieces.
To Make the Miso Sauce
In a small bowl, combine 5–6 Tbsp miso, 4 Tbsp sake, 2 Tbsp mirin, and 1 tsp soy sauce and mix it all together.
To Pre-Cook the Hot Pot in the Kitchen
The kombu in the donabe should be rehydrated in water (this is kombu dashi). Add the potatoes, daikon radish, and corn into the broth.
Cover the donabe and bring the broth to a gentle simmer over medium heat. Discard the kombu (you can repurpose the used kombu to make simmered kombu or homemade furikake rice seasoning).
Cover and continue to cook for 10–15 minutes until a wooden skewer goes through daikon radish.
Add two-thirds of the miso sauce into the hot pot broth and mix well. Set aside the rest of the miso sauce and add it to the broth after everything is cooked through.
Taste the broth. If you want a stronger miso flavor, add more miso. Instead of dropping the miso into the broth, take out a small portion of the broth into a bowl, add miso, and let it dissolve completely before returning back to the broth. Season the broth with ¼ tsp Diamond Crystal kosher salt to your taste.
To Cook the Hot Pot at the Table
Set up the table with a portable stove, platters of ingredients, individual bowls, and cooking utensils (long chopsticks, a ladle, and a fine-mesh skimmer). Add some of the ingredients to the donabe and cover to cook for 10 minutes.
Once all the ingredients are cooked through, add the rest of the miso sauce and put 2 Tbsp unsalted butter on top. Pick up the cooked ingredients and serve in individual bowls to enjoy. Sprinkle Japanese sansho pepper to your taste. Once the hot pot is almost empty, add the next batch of ingredients and continue cooking and eating.
To Store
You can keep the leftover salmon hot pot in an airtight container and store it in the refrigerator for 2 days.