Heat the sesame oil in a large pot over medium heat;add the garlic and ginger, and cook for a few minutes until softened. Add the soy sauce and stir to combine.
Add the chicken stock, mushrooms and chicken. Bring to a boil and simmer for 5 minutes.
Add the Udon noodles and cook for 3-4 minutes (or according to package directions).
Stir in the green onions.
Serve and enjoy!
With the stock, a stronger flavor is better. Weak stock makes for a weak tasting soup. DO NOT add salt until you taste it at the end, then season if you want. The chicken stock is usually salty enough! DO try and use fresh Udon noodles, it makes all the difference!