Soak the cashews in boiling water for at least 10 minutes.
Wash and slice the mushrooms, and chop the onion, parsley, and thyme.
Heat the olive oil in a large pan, add the chopped onion and minced garlic cloves.
Add the sliced mushrooms, half of the chopped parsley, and thyme, and stir regularly. Season with salt and black pepper and let them cook for about 10 minutes, until soft and wilted.
In the meantime, cook the pasta in salted boiling water according to the package direction. Reserve 1 cup of the cooking water before draining.
Rinse the cashews under running water. Make the cashew cream by blending the soaked cashews with water, lemon juice, and salt.
Add the cream to the cooked mushrooms, and stir well. Transfer the pasta into the sauce, toss for 1-2 minutes. If the sauce is too thick, add a bit of the reserved cooking water.
Garnish with the remaining parsley and thyme, grated walnuts, or parmesan.