Cut the beef in thin slices and marinate it in a bag with the soy sauce for 30 minutes.
Cut the carrots, onion and the mushrooms in thin slices.
Cook the udon noodles according to the package and let them rest in ice water until it is time to serve.
In a frying pan cook the beef in the olive oil for approx. 5 minutes.
Add the vegetables and sesame seeds and cook for 3 more minutes.
Pour the menstsuyu sauce on and stir together.
Place noodles on a plate and the beef teriyaki on top. If desire add some more mentsuyu sauce on the beef. Another option is to have some sauce in a small bowl on the side to be able to dip the food in.