Place all marinade ingredients in a mixing bowl. Mix until everything is combined. Set aside.
Heat vegetable oil in a non-stick skillet over medium or medium-high heat (See notes).
When the oil is hot enough, add marinated beef. Quickly stir for 1-2 minutes until the outside of the meat is cooked evenly.
Add minced garlic to the skillet (if desired). Stir or shake the pan vigorously for another minute.
Finally, add bell peppers and white onion, followed by unsalted butter, and stir/shake until the vegetables are almost entirely cooked, about 2-3 minutes.
Turn off the heat. Remove the skillet from the stove immediately to avoid carry-over cooking.
Transfer sauteed beef to a bed of potato chips on a serving dish. Garnish with green onion.
Serve immediately with a hot bowl of steamed rice or by itself.