1. Preheat oven to 450 degrees Fahrenheit (230 degrees Celsius).
2. Heat two tablespoons oil in a frying pan over medium-low heat. Add onions to pan and sauté until they develop a deep amber color. Transfer to a bowl and set aside.
3. Raise heat to high. Add sliced steak to the pan and let it get a nice crust, then transfer to the bowl of onions. Immediately, add scallions to the bowl too, so they wilt a drop from the heat of the steak.
4. Add more oil to the pan if necessary and sauté shredded carrots for one to two minutes.
5. Lay the cabbage in a single layer on two baking sheets. Season with salt and pepper and drizzle with oil. If using garlic, sprinkle it over the cabbage. Place the baking sheets in the oven and roast 10 to 15 minutes.
6. Remove cabbage from oven. Combine with steak, sautéed onions, and carrots just before serving.