1Blend cashews and 1 cup vegetable broth in a blender until smooth, about 1 minute.
2Pour the remaining 4 cups vegetable broth into a large pot; add potatoes and onion. Bring to a simmer, cover, and cook for 5 minutes. Stir in broccoli and basil; return to a simmer. Cover and cook until potatoes are tender, about 10 minutes.
3Stir cashew mixture into soup; add salt and black pepper. Bring to a simmer and immediately remove from heat. Transfer about half the soup to a blender; blend until smooth. Return blended soup to pot and stir well. Serve immediately.
Footnotes
Tip
Aluminum foil helps keep food moist, ensures it cooks evenly, keeps leftovers fresh, and makes clean-up easy.