Pour water, add kombu in a pot and heat on low flame. Take off kombu just before boiling. When boiled, add flaked dried bonito and boil for 2 min, then turn off the fire. After dried bonito sank in a pot, strain the stock.
Put 1. and A in nabe.
Slice mushroom. Boil spinach and cool in water and drain. Cut into bite-size.
Slice long green onion, kamaboko, chop chicken thigh into bite-size.
Put udon in 2., top with 3., and 4., then cook on high flame.
Lower the heat when boiled, drop egg and cover the lid, simmer for 1 min. Put Shichimi-tougarashi (Japanese red pepper) as you like.