Place a large pan over medium heat and drizzle with about a tablespoon of oil.
Once heated, add the sliced onions and cook, stirring often, until softened.
Stir in the meat, season with salt and pepper, and continue to cook, stirring occasionally, until golden on all sides.
Add the carrots, potatoes, cabbage if using, and garlic. Cook until starting to soften.
Pour the water into the pan and bring to a boil. Reduce to a simmer and arrange the sliced noodles around the top, leaving a hole in the center. Drizzle the tops of the noodles evenly with about 1 tablespoon oil. Cover tightly with a lid and steam the noodles until cooked through, about 15 minutes. If the water has evaporated before the noodles are finished cooking, pour in a little more water.
Once cooked, remove the lid and gently fan the the noodles using a paper fan, the pot lid, or even a cutting board to help dry out the top layer.
Use a fork to gently fluff and separate the noodles, then lightly toss all the ingredients together. Season to taste with salt and pepper and serve immediately topped with the green onions.