Blend onions with 4 cups of water and add to a soup pot. Blend broccoli with remaining 4 cups of water and add to the soup pot. Simmer for 1 hour. Add vegetable broth, blend and return to the pot.
Blend cashews, cayenne, nutritional yeast, and vinegar together and add to the pot. Return to a simmer. Add chia seeds and broccoli and cook for 45 minutes.