In a measuring cup, stir together soy sauce, mirin, and honey. Set aside.
Chop the steak into bite size pieces, then sprinkle all sides with Kosher salt and pepper.
Heat a large cast iron or stainless steel skillet over medium high heat. Add enough oil to coat, and heat until shimmering.
Spread the steak bites evenly across the pan and sear, undisturbed, for about two minutes. Flip and continue to sear about 1 minute.
Add the garlic and butter and toss to melt.
Add the sauce, and continue to cook, stirring often, until the sauce is slightly thickened and steak is well coated, 1-2 minutes. NOTE: This steak does not need very long to cook! 4-5 minutes total is all you need for a medium steak, so remove it promptly after adding the sauce.
Remove from heat and serve with yum yum sauce, if desired.