Cut the steak into 1-inch pieces. Toss with steak spice.
Preheat a 10-inch cast iron skillet over medium-high heat. Add 1 tablespoon vegetable oil.
Add half of the steak steak in a single layer and cook for 2-3 minutes without stirring. Stir and cook 1 minute more, transfer to a plate. Repeat with the remaining steak.
Remove the hot skillet from the heat and add the butter and garlic (the residual heat will be enough to cook it without burning). Cook for 1 minute or until fragrant.
Add the steak (with any juices) and parsley to the skillet and stir to combine, scraping any bits off the bottom of the pan.
Immediately transfer to a plate and season with additional salt if desired.
Notes
Although this recipe recommends cast iron, steak bites can be made in any pan.
To make in advance, cut steak into bite-sized pieces, season, and store uncovered in the refrigerator. The surface will slightly dry out and the meat will sear more easily.