Let steak stand at room temperature 30 minutes. Cut into bite-sized pieces, about 1-inch. Season with salt and pepper.
Heat a 12-inch heavy or cast iron skillet over medium-high heat. Add oil. Add steak bites to skillet, in batches if needed (do not crowd the skillet). Cook 2 minutes on each side until well browned but still pink in the center. Remove steak bites from skillet, keep warm. Turn off heat.
Wipe out skillet using wet paper towel held with tongs. Melt butter in the skillet over medium-low. Add garlic and cook until fragrant, about 1 minute. Drizzle over steak bites. Sprinkle with chives.
