1. Soak the dried shiitake mushrooms in warm water to rehydrate for at least 15 minutes. You only need just enough water to cover the mushrooms. You can place a smaller bowl on top to keep the mushrooms submerged under water.
2. Squeeze the excess water out of mushrooms. Cut off the stems if there are any and score a cross on top. Reserve the leftover soaking liquid (shiitake dashi) for the udon soup broth (strain the dashi through a mesh strainer to remove any grit or impurities before using).
3. Blanch the spinach in lightly salted boiling water for 1 minute (starting stem side first).
4. Slice the carrot (if you want, you can cut out the carrot into a flower shape with a vegetable cutter like I did).
5. Cut kamaboko into thinly slices and break shimeji mushrooms into small pieces.
6. Slice naga negi diagonally and cut the chicken into 1” pieces.
7. To make udon soup, combine dashi soup and dashi from dried shiitake mushrooms in a small saucepan. Bring it to a boil over medium high heat.
8. Once boiling, add mirin, soy sauce, and salt. When boiling again, turn off the heat and set aside.
9. If making your own shrimp tempura, prepare, batter, and fry your shrimp (follow link to directions). Set aside for later use.
10. Cook udon in boiling water. Once the noodles are separated, take them out and soak in ice water to prevent them from cooking further. Drain and set aside.
11. Place noodles in large nabe pot, and then arrange the rest of the prepared ingredients (except for egg, spinach, and mitsuba). If using two smaller individual nabe pots, split the noodles between the two bowls and then divide the remaining ingredients between them.
12. Add udon soup to the pot and cover with the lid. Bring the soup to a boil over medium high heat. When it comes to a boil, leave the lid slightly open to let some steam out, or it will overflow. Lower the heat and simmer to cook until the chicken is cooked through.
13. Add egg, spinach, and mitsuba and cover to cook until the egg is done to your liking.
14. Place shrimp tempura on top and serve. Sprinkle shichimi togarashi on top if you like your soup a bit spicy.