Bring a medium-sized pot to a medium heat with organic canola oil, or other neutral-flavored oil. Add chopped onions and minced garlic. Saute a few minutes, until translucent and fragrant.
Add cooked chestnuts, dried rosemary, and dried thyme to the pot. (If the chestnuts are stuck together, break them apart with your hands as you put them into the pot.) Saute for about a minute.
Add water, Better Than Bouillon no chicken base, pinch of salt, and dash of pepper. Stir to evenly incorporate everything. Cook for a couple minutes.
Add cashew cream to the pot, and stir to evenly combine everything. Cook for a couple minutes more.
Now it's time to blend the soup until creamy. If you have an immersion blender, I recommend using that, so that you're not moving hot liquid. Blend until completely smooth with a stick blender. If necessary, continue cooking for a minute or so more, until the gravy is the thickness you like. (If it's not thick enough or warm enough, keep letting it cook until it condenses more. If it's too thick, add a splash of water.)If you don't have an immersion blender, carefully put the soup into a standard blender, and blend until smooth. If it's not thick enough or warm enough, put the soup back into the pot, and continue cooking until it's reached your preferred thickness/warmth.