Make the cashew cream by soaking the cashews in enough hot water to cover and allow them to sit for 30 minutes. Drain, rinse and add them to a blender. Add 1/2 cup water and a pinch of salt before blending until completely smooth and creamy. Add more water as needed until you have a rich creamy blend. Set aside. (can be made a day or two before)
Heat the vegan butter in a large pot on medium heat. Once melted add in the onions and thyme then sauté for 3-5 minutes or until onions become translucent.
Roughly chop the mushrooms leaving some whole slices and add them to the pot. Cook until they begin to brown and break down about 5-8 minutes. Add in the garlic and cook for another 2 minutes or until the garlic is fragrant.
Add the miso paste and mix until dissolved. Add in the vegan beef broth, mix well and simmer 20 minutes.
Pour in the cashew cream and mix through. Simmer on low heat for an additional 8-10 minutes. The soup should thicken a bit before serving.