At least an hour (and up to 24 hours) before you want to make the sauce put the cashews into a heat proof bowl or jug and cover with boiling water. Set aside until you're ready to use them
When you're ready to make the sauce peel the onion and dice finely. If you're cooking the garlic with the onion, peel the cloves and crush in a garlic press. Add both the onions and garlic to a medium pan along with a drizzle of olive oil and saute for 1-2 minutes until softened
Add the mushrooms and thyme leaves and cook, stirring occasionally for a few minutes until cooked through
While the mushrooms are cooking drain off and discard the water from the cashews and put the nuts into a blender cup
Add the veg stock and nutritional yeast and whizz everything together until blended and creamy
When the mushrooms are cooked pour in the cashew sauce and warm through. Taste and add salt and pepper as needed
Serve immediately or chill in the fridge until required
When stirring this sauce through cooked pasta I add a little bit of the pasta water to the sauce to thin slightly but if using as a 'gravy' I prefer to keep it thicker
Notes
You can sub the chestnut mushrooms for normal closed cup mushrooms or even portobello mushrooms. I used the chestnut as they have a slightly firmer texture once cooked and a lovely earthy flavour!
Recipe by The Cook & Him at https://thecookandhim.com/recipes/mushroom-sauce/