Prepare the cashew cream by blending the soaked and drained cashews with vegetable broth, nutritional yeast, and lemon juice until completely smooth. Set aside.
Cook your pasta according to package instructions until al dente. Drain and set aside, tossing with a little olive oil to prevent sticking.
Heat olive oil in a large skillet over medium-high heat. Add the seitan strips and cook until they develop a golden-brown crust, about 5 minutes. Remove from pan and set aside.
In the same pan, add the sliced onions and cook until translucent, about 3-4 minutes. Add the minced garlic and cook for another 30 seconds until fragrant.
Add the mushrooms to the pan and cook without stirring for 2-3 minutes to allow them to brown. Then stir and continue cooking until they release their moisture and begin to caramelize, about 7-8 minutes total.
Pour in the white wine (if using) and scrape up any browned bits from the bottom of the pan. Let it reduce by half, about 2 minutes.
Add the tamari, Worcestershire sauce, paprika, and thyme to the mushroom mixture, stirring to combine. Cook for 1 minute to allow the spices to bloom.
Return the seitan to the pan and stir to combine with the mushroom mixture.
Reduce heat to medium-low and pour in the cashew cream, stirring constantly to incorporate. Allow the sauce to simmer gently for 5-7 minutes until it thickens to your desired consistency.
Taste and adjust seasoning with salt and pepper. The tamari adds saltiness, so taste before adding additional salt.
Serve immediately over the cooked pasta, garnished with fresh parsley.