- Combine the mirin seasoning and soy sauce into a small bowl with the beef slices and mix well. Allow to marinate (up to 1 hr).
- Heat a griddle pan or BBQ over a medium heat for 2 mins and sear beef for 1 min on each side. Remove and set aside.
- Heat the beef broth or miso soup in a saucepan; then add the udon noodles. Loosen noodles with a fork and let noodles heat through. Stir in the oyster mushrooms and heat 2 mins.
- Serve broth, udon noodles and mushrooms in a small bowl.
- Top with the beef slices and serve, garnish with spring onions.