Combine all the ingredients for the cashew cream in a high-speed blender. Blend on low for 20 seconds, then on high for 40 seconds, until it forms a smooth creamy liquid.
Heat olive oil in a large skillet over medium heat.
When the oil is hot, add the onion and garlic. Stir until just transparent, about 2 minutes.
Add the mushrooms. Stir and cook until the mushrooms are just cooked through, about 5 minutes. If the mushrooms stick to the pan at any time you can add the tablespoon of sherry, vegetable stock, or water and scrape the mushrooms free.
Stir in the soy sauce and blended cashew cream. Reduce the heat to medium-low. Bring to a simmer and taste the sauce. Add salt as needed. Stir in some the mushroom soaking water or pasta boiling water if you need to thin out the sauce.
Add pasta into the skillet with the sauce. Use tongs or chopsticks to stir the pasta and coat it thoroughly with sauce. Simmer until the pasta is heated through.
Garnish with parsley, thyme, and black pepper and serve immediately.