Get a pot of salted water to a rolling boil and add the dry pasta. Cook according the the packaging instructions. Set aside. Once cooked, drain the pasta reserving some of the pasta water in case needed.
Place your dehydrated mushrooms into a small bowl of boiled water and allow to re-hydrate.
To a deep pan or dutch-oven add vegan butter, minced shallot and minced garlic. Stir around for about 2 minutes until golden. Add the sliced portobello mushroom and white mushrooms. Toss until coated in butter. Place the lid on the pot until the mushrooms are soft.
Add the flour and toss until the flour starts to look like a paste. You may need to add a touch of water to get this consistency. Add the non-dairy milk and 1/2 cup of the mushroom water from the dehydrated mushrooms. Mix until incorporated. Add nutritional yeast and thyme.
Slice the dehydrated mushrooms and add those to the sauce as well. Stir until incorporated. Cook until just thickened, you still want to be able to pour it smoothly.
Add the cooked pasta to the sauce and add any pasta water to thin out if needed. Top with some fresh parsley, serve with garlic bread and you're good to go.