Udon are thick white noodles made from wheat flour that are used in Japanese cooking. Look for them in the Asian section of the supermarket. Or use 200 g medium rice noodles instead – just soak them in hot water for 5 min before adding to the soup.
If you have a mini ice cream scoop, use it to easily scoop meatball mixture straight into boiling soup. If you don’t have one, we rolled the meatball mixture into a log and cut it instead of just rolling into balls, because we found this method was much faster.