1. Making the kakiage In a large bowl, add leeks and shrimps. Mix. Then add katakuriko/potato starch and flour. Coat vegetables well with flour.
2. For tempura batter, add beaten egg in a medium bowl, then add ice water (2 tbsp) and vinegar (1tsp). Mix them. Pour the batter on the vegetables from #1 and mix lightly.
3. Prepare a large plate lined with paper towels (it will help absorb excess oil).
4. Add oil to a large saucepan to reach a depth of 5 cm. Heat up to 165~170°C at medium-high heat. Gently place a few battered vegetables in. While the batter fries, use your chopsticks to maintain the veggies shape until it has hardenned (other wise they might spread away from each other). Fry kakiage until they are golden brown. Drain excess oil on the paper towel plate. Set aside.
5. Prepare the udon soup In a big cooking pot add 2L water, add soy sauce, mirin, sugar, salt and dashi powder. Bring it to a boil. That's your soup.
6. Bring another large pot of water to boil for udon cooking. Once the soup and the kakiage are ready, cook udon noodles in the water. For the time to boil udon, follow the package instructions. Heat up the noodle soup at the same time.
7. Serve udon and soup in bowls and top with kakiage!