Heat olive oil in a large pot over medium heat. Add the diced onion and cook until translucent, about 5 minutes. Then, stir in the minced garlic for the last minute until fragrant.

Toss in the diced carrots, zucchini, and sliced mushrooms into the pot. Sauté these colorful veggies until they're tender and slightly browned, about 7 minutes.

Pour in the low-sodium vegetable broth and the canned crushed tomatoes. Season with dried herbs, salt, and pepper. Bring to a gentle boil before reducing the heat to simmer for about 15 minutes.

Drain the soaked cashews and place them in a blender with fresh water. Blend until smooth and creamy, creating a delightful cashew sauce.

Mix half of the creamy cashew sauce into the soup for a luscious texture. Serve hot, garnishing with the remaining cashew sauce and fresh basil if desired.