(Skip if making this OIL FREE) Add 1 tablespoon of oil to a large wok over medium-high heat. When the oil begins to shimmer (around 1 minute), add the vegan steak. Cook until browned (around 2 to 3 minutes). Remove from wok and drain excess oil on paper towel. Set aside.
(Add vegetable broth if making this OIL FREE) To the same pan in which you cooked the vegan steak, add onions and garlic (and mushrooms, if substituting for vegan steak). Sauté until the onions begin to brown (around 3 minutes). Create a well in the center of your wok and add 1 tablespoon of oil (or vegetable broth). When the oil begins to shimmer (around 30 seconds), add jjajang paste. Gently sauté the paste in the oil until it becomes extra glossy.
Next, add the zucchini, potato, and cabbage and continue sautéing until zucchini begins to get soft (around 2 minutes). Season with salt and pepper. Incorporate the stir-fried vegetables into the paste until evenly coated. Deglaze the pan with soy sauce and add sweetener. Stir the contents of the pan until the vegetables are glossy.
Add vegetable broth and bring to a boil. Then lower heat to low and let the contents simmer until the potatoes are fork tender (about 15 minutes). While the sauce is stewing, create a roux by whisking together the potato starch with 1/4 cup of water. When the potatoes are just about cooked, add frozen peas, the vegan steak that was removed at the beginning, and the roux. Continue stirring over low heat until the sauce thickens into a gravy consistency. Pour over cooked noodles and enjoy with pickled daikon, kimchi, and raw onions.