Cook the udon noodles in boiling water for about 5 minutes. Then rinse with cold water and set aside.
In a large pan or wok, cook the onion over medium heat until translucent, about 5 minutes.
Add the mushrooms and peppers and cook for about 5 more minutes or until the peppers are soft.
While the mushrooms and peppers are cooking, whisk the sauce ingredients together in small bowl.
Add the carrots and edamame to the wok and cook for a minute or two.
Add the bok choy, and cook until the leaves start to wilt.
Add the sauce to the pan, and mix everything together to coat. Let cook for a minute or two to heat throughout, then add the noodles and toss to coat. The noodles should soak up some of the sauce.
Remove the pan from the heat and sprinkle with the sesame seeds.