Bring a medium pot of water to a boil, and salt well (until it tastes like sea water--I used about 2 tsp salt for about 3 inches of water). Cook noodles until al dente, strain the noodles but reserve at least 1 cup of water from the pasta.
In a large pot over medium heat, cook the vegan ground substitute until browned, breaking up the pieces to your desired sized chunks. (See YouTube video for what I did). Stir well to get an even browning, this should take about 5 minutes.
Once browned, add diced onion, and cook until onion is softened, about 3-4 minutes. You might need to splash on some water to deglaze the bottom of the pan and lower the heat if you find that the ground is sticking too much. Add crushed garlic once the onion is cooked, and stir for about 30 seconds, until fragrant.
Add 2 tbsp of flour (or cornstarch), and add just enough water to hydrate the flour to create a roux. Once the flour is hydrated, add about 1 cup of the pasta water and the broth paste, and mix to incorporate.
Add in the cooked pasta and stir to coat. Check that everything is cooked to your liking (pasta and the vegan ground beef), then add in the vegan sour cream and parsley.
Turn off the heat and serve immediately!