Cook 2 portions udon noodles according to the instructions on the packaging.
In a medium saucepan, add 500 ml dashi stock, 1 tsp salt, 1 tsp soy sauce, 1 tsp mirin, and ½ tsp ginger paste. Mix everything together and bring to boil. Once boiling, lower the heat to simmer.
Take a small bowl and make a slurry by mixing 1 tbsp cold water with 1 tbsp potato starch. Pour the slurry into the broth and mix thoroughly.
Add the chicken and 30 g Japanese leeks (naganegi) to the broth. Make sure to pour in the chicken juices from the frying pan for extra flavor.
Turn the heat back up to medium and bring to a boil once more. While you're waiting for it to boil, crack 2 medium egg(s) into a bowl and whisk them thoroughly.
Once the broth starts to boil, drizzle in one third of the whisked egg. The egg will reduce the temperature of the broth, so wait for it to start bubbling again before adding the next third. Repeat until all of the egg is in the soup, then mix and remove from the heat.
Rinse the cooked udon with boiling water and then divide into two serving bowls, then pour the broth over the noodles.
Garnish with chopped finely chopped green onions and Japanese chili powder (shichimi togarashi) (optional).
Enjoy!