Step 1

In a bowl or liquid measuring cup, whisk together the soy sauce, mirin, sake, sugar, and 2 tbsp water. Whisk in the cornstarch and set aside.

Step 2

In a large, non stick frying pan, heat up the oil over medium heat. Add the onions and cook, stirring, until soft, but not browned.

Step 3

Add the thinly sliced beef to the pan and cook, until just cooked through. Add the sauce to the pan and bring to a gentle simmer, letting it bubble, thicken, and reduce.

Step 4

When the teriyaki sauce is glossy and coats the beef, remove from the heat and serve over fluffy white rice. Top with toasted sesame seeds and sliced green onions. Enjoy!