Trim stems off bok choy. Place bok choy in bowl of cold water and swish around to remove any dirt or sand. Cut bok choy into rough pieces.
Bring broth to a boil. Add bok choy and kelp noodles. Cook for a minute or two until bok choy is tender. Baby bok choy only takes a minute. Regular bok choy will take a little longer because the stems are thicker.
Transfer noodles, bok choy and broth to a bowl. Cut open soft boiled egg and place on top.
Drizzle sesame oil on top. Sprinkle some sesame seeds on top, if desired.