How to Make It
In a medium bowl, toss the pork with the soy sauce and season generously with pepper. Refrigerate for 15 minutes.
Heat a large cast-iron skillet until smoking, then add 1 tablespoon of the oil. Add the pork and cook over high heat, undisturbed, until browned on the bottom, about 2 minutes. Stir-fry until the pork is just cooked through, about 2 minutes more. Transfer to a plate.
In the skillet, heat the remaining 2 tablespoons of oil until shimmering. Add the celery and chiles and stir-fry over high heat until the celery is crisp-tender, 2 to 3 minutes. Return the pork to the skillet, season with salt and pepper and toss to combine. Serve immediately.