Sauce - whisk and combine all the sauce ingredients in a bowl or measuring cup. Set aside.
Soba noodles - Cook noodles as per packaging instructions. I usually add them to salted boiling water, reduce the heat to medium and cook for 5 minutes. Remove from water and rinse under cold water to stop the cooking process. Add a little bit of vegetable oil and toss. Set aside.
Stir fry - Heat up a bit of vegetable oil in a wok or regular medium pan (high heat). Add onion, cook for few minutes and follow with ginger and garlic.
Fry for couple seconds until fragrant. Add mushrooms and carrot (a bit later, after few minutes). Stir fry in total about 3-5 minutes or until mushrooms become golden brown.
Reduce the heat to medium, stir in the noodles and pour over the sauce. Toss to combine and stir fry for 2 minutes. Remove from heat and serve immediately.
Garnish with more sesame seeds, edamame (i simply thawed my frozen edamame until room temperature and added to the noodles later, alternatively you can add them together with carrot), fresh chili pieces (remove the seeds prior), chopped spring onion/scallions.