Ishikari Nabe (Salmon and Miso Hot Pot)

Name: Ishikari Nabe (Salmon and Miso Hot Pot)
Prep time: 30 min
Cook time: 15 min
Total time: 45 min
Cuisine: Japanese
Ingredients: 600 ml water; 3 g dried kelp (kombu); 1 tbsp soy sauce; 1 tbsp sake; 1 tbsp mirin; 3 tbsp yellow miso paste (awase miso); 1 potato (waxy type, peeled and thickly sliced); ½ carrot (peeled and cut into thick rounds); 4 leaves napa cabbage (roughly cut); 2 shiitake mushrooms (or mushrooms of choice); ½ yellow onion (sliced); 200 g firm tofu (cut into large cubes); ½ Japanese leek (naganegi) (thinly diagonally sliced); 2 salmon fillets (skin-on); 6 scallops; 1 tbsp butter; sansho pepper; cooked udon noodles (optional to finish the soup)