Chop onion, garlic, and zucchini.
In a large soup pot, sauté onion and garlic gently in olive oil until softened and fragrant.
Add miso paste and thyme and stir to coat onions.
Add zucchini, cashews and water. Bring to a boil then reduce heat and simmer until zucchini is soft, about 15-20 minutes. Add water if necessary to keep zucchini covered.
Remove from heat and let stand until cool enough to purée.
Purée soup in batches in blender – be sure cover of blender is on tight as steam from soup could pop lid.
Season with salt.
Ladle soup into bowls and top with fresh herbs.