1. Heat the olive oil in a large pot over medium heat. Add the onion and garlic and sauté until soft and fragrant.
2. Add the vegetable broth and non-dairy milk, increase the heat to medium-high, and bring to a boil.
3. Add the fettuccine to the pot and cook uncovered for the amount of time suggested on the package or until the noodles are cooked and tender. Stir the pasta frequently to prevent it from clumping or sticking to the bottom of the pan.
4. While the pasta is cooking, mix the cornstarch and 2 tbsp of water in a small bowl until the cornstarch dissolves.
5. Two minutes before the pasta is done, add the cornstarch/water mixture, salt, and ground black pepper to the pot. Cook for 2 to 5 minutes, until the sauce starts to thicken.
6. Turn the heat off and allow the pasta and sauce to rest on the stove for 5 minutes to thicken. If the sauce is still very liquidy, turn the heat on while mixing the pasta and sauce for another 1 to 2 minutes—but keep in mind that the sauce will continue to thicken with time.
7. Plate the pasta and garnish with the cracked black pepper and parsley as desired.