Season the oxtail with about 2 tsp. salt and pepper, or to taste. Heat grapeseed oil (or oil of choice) in a pot or dutch oven over medium-high heat and add half of oxtail. Brown on all sides. Do the same with the second batch. If your pan isn’t big enough, you can do it in three batches. Just make sure not to crowd pan or the meat won’t sear properly nor will it have a nice crusty brown skin. Remove and set aside.
Add aromatics, spices, and braise.
Add another dab of oil to the same pot and add garlic, ginger, and the white parts of the scallion. Cook over medium heat until for 2-3 minutes or until fragrant. Add the oxtail back into the pot along with 1 tbsp. tomato paste, ½ tsp. five spice, 1 tsp. sugar, 3 whole star anise and stir to combine. Add ¼ cup soy sauce and ¼ Shaoxing wine along with 32 oz. of chicken broth. Bring the mixture to a boil, then cover and braise on low heat for at least 2½ hours.
Discard bones, shred meat.
When the oxtail is done braising, the meat should be tender and falling off the bone very easily. Using tongs, discard all the bones. Shred the meat on a chopping board with a fork or alternatively, you can cut it up with a knife, depending on how chunky you want the meat. Return meat back into pot with braising liquid.
Once the bones are discarded and the meat pieces have returned to the pot, add the shiitake and shimeji mushrooms and cook on medium heat for another 10 minutes, or until mushrooms have cooked through.
Make cornstarch slurry.
Make a cornstarch slurry by adding about 2 tbsp. of water to your 2 tbsp. of cornstarch in a small bowl. This will allow the cornstarch to mix into your braising liquid smoothly without lumps. Do not put cornstarch straight into the hot braising liquid! Once you’ve made your cornstarch slurry, add the whole mixture to the pot and stir immediately. Bring to a boil and continue mixing for about 30 seconds. The liquid should begin to thicken and become saucey. Salt and pepper to taste.
Meanwhile, follow the instructions from the packet and cook your noodles. Drain in a colander once noodles are al dente and plate in serving bowls.
Assemble and serve.
Ladle the sauce over your noodles directly, or if you want to mix the sauce and noodles before serving, you can do so in either another mixing bowl or pot. Garnish with chopped scallions or chili flakes if desired. Serve immediately. Congrats! You just made Braised Oxtail Noodles.