Set a large, heavy skillet over medium-high heat. Add the oil and when it's hot, add the beef, sprinkling it with salt and pepper in the pan. Turn to brown on all sides - you just want to get some colour - then transfer to a braising dish or slow cooker.
Pour the orange juice into the pan and stir to scrape up any browned bits - pour over the meat. Add the ketchup, soy sauce, ginger, garlic and chili, stir to combine, cover and braise in the oven at 300F for 2 1/2-3 hours, or cook on low in the slow cooker for 6-8 hours.
If it's too saucy and you'd like to thicken it up, stir the cornstarch into 1 Tbsp. cold water, add to the meat mixture and bring to a simmer until it thickens. Otherwise serve it as-is, with flour or corn tortillas, chopped purple or green onion, and fresh cilantro for serving.