Pour the oil into a large, shallow pot and place on high heat on your stove top, making sure the pot is big enough to fit the whole length of your spaghetti comfortably.
You can snap your spaghetti in half if need be.
Add the onions and garlic to the pan and stir frequently to prevent burning.
Fry until onions are soft, about 2-3 minutes.
Add mushrooms and stir frequently, frying until golden brown and soft.
Add the paprika, mustard powder, dried thyme, salt, nutritional yeast and spinach and mix well.
Lay the spaghetti in the pot over top of the onion and mushroom mix.
Pour 2 cups of the milk (keep the last ½ cup for later) over the spaghetti, followed by the vegetable stock.
Sprinkle with freshly ground pepper to taste.
Bring the pasta mix to a boil and then reduce the heat to a gentle simmer.
Cover and let the sauce simmer for 8 to 10 minutes or until the pasta is cooked and sauce has reduced to a creamy consistency.
Stir every couple of minutes to stop the pasta from sticking together.
Once pasta is cooked and the sauce is looking silky smooth, remove pot from heat and stir in the remaining ½ cup milk.
Serve immediately, topped with chives, spring onions and vegan parmesan if desired.