Heat vegetable oil in a large skillet or hibachi grill over medium-high heat.
Season the steak cubes with salt and pepper.
Add the steak to the hot pan and sear until browned on all sides.
Push the steak to one side and add butter, garlic, and ginger to the pan.
Sauté until fragrant, then mix with the steak.
Drizzle soy sauce and sesame oil over the steak and toss to coat.
Optional: Add mirin for extra depth of flavor.
Garnish with chopped green onions and sesame seeds before serving.