Season the roast on all sides with pepper. You will not need to salt the roast.
Heat the oil in a large stock pot and then sear the roast on all sides until a nice brown crust develops. Remove the roast and set aside briefly.
Deglaze the pan with the red wine vinegar and use a spoon to scrape the bits off the bottom of the pan.
Add 4 cups of the beef broth and 4 cups of water to the pot. Add the mushrooms, dried onions, bay leaves, and soy sauce as well. Stir the ingredients and then return the roast to the pan.
Bring the liquid to a rolling boil and then reduce the heat to a low boil. Cover the pot until the liquid has reduced by half. This should take about 45-60 minutes.
Add 4 more cups of beef broth and 4 more cups of water to the pot. Return the liquid to a low boil and re-cover the pot. Again reducing the liquid by half. (Around 45-60 minutes.)
Test the roast to see if it pulls apart easily. It should be soft and easily shredded by this point. Take a test bite to see if the texture is to your liking. If not, add more water back to the pot, cover, and bring to a low boil until your roast reaches the desired texture.
Remove the roast from the pot and shred with forks, taking care to remove any fat or gristle. Set the shredded meat aside.
Strain the remaining liquid with the fine mesh strainer into a large bowl. This will remove the spices and mushrooms and will make the gravy extra silky. Return the liquid to the pot and set the heat to low.
In another pot, prepare your noodles per the instructions on the bag. Strain and set aside.
Put 1 1/4 cups of water in the measuring cup and add the 8 Tbsp of corn starch. Stir until a slurry forms.
Slowly whisk the corn starch slurry into the boiling liquid, stirring constantly. Continue to whisk often until the liquid starts to bubble and thicken.
Once the liquid has thickened, return the shredded beef to the pot and stir to incorporate. Let the mixture bubble for 2-3 minutes to re-heat the beef.
To serve, you can place the noodles into a bowl and pour the sauce and beef over it or you can combine the noodles with the sauce and beef within the pan before serving.