Boil the udon noodles in a pot (you can use dried or fresh). Transfer the hot noodles directly from the pot to your dish.
Place the fresh egg on the top-center of the udon, sprinkle with the shredded nori, pour in the dashi soy sauce, and mix it up with chopsticks to finish. Garnish with shredded nori and sesame seeds to taste.
Those who are living overseas (like me) can't eat raw eggs, so you can also use poached or soft-set eggs (these are half-cooked too, so they're still probably not the best to have, but we eat them up anyway).