In a saucepan over medium heat, add the oil. Once it's hot enough, add in the garlic and onion.
Sautee these together until the onions are becoming tender - for about 2 minutes.
Add in the rest of the ingredients, EXCEPT the cashew milk, veggie broth and cornstarch.
Allow the mushrooms to sautee in the spices for a few minutes. I would give this maybe 4-5 minutes.
In a separate small bowl, whisk the cornstarch into the veggie broth so it doesn't cause clumps in the soup.
Whisk the cashew milk and the broth + cornstarch mixture into the soup.
Whisk to incorporate all ingredients, and turn the heat to medium-high to allow it to come to a boil.
Once it boils, keep stirring it and reduce the heat to low, to let it simmer for about 15-20 minutes. The soup will thicken a lot! Stir it every couple minutes (I would say every 2 minutes).
Once the soup is thickened, flavor it with any other seasonings to taste, and turn off the heat. Enjoy hot! See storage details below.