If using fresh broccoli, remove and discard tough lower stalk, and peel remaining stalk. Chop stalk and florets into small pieces.
Spray a large skillet with cooking spray and add onion. Cook for 8 to 10 minutes, until tender.
Add water or vegetable stock, broccoli, potato, and some salt and bring to a boil. Reduce heat and simmer until vegetables are very tender, about 15-20 minutes.
Remove soup from heat and save a few florets for garnish. Purée with a hand-held blender until smooth. Or, working in batches, transfer to a standing blender to puree. Never fill your blender more than ½ full. Also, remove the center cup on the two-part lid and cover the opening with a kitchen towel to allow hot air to escape and prevent pressure from building up. Hold the lid down tightly with a towel. Return the soup to the pot and season to taste.
To make cashew cream (optional step), blend 2 ounces of raw cashews with about ½ cup water in high-powered blender until very smooth, and pour into the soup. Bring to boil.
To serve, put a few tablespoons of quinoa into each serving bowl and pour the soup over. Garnish with broccoli florets or fresh dill or parsley. This recipe serves 2-4, depending on the portion size (side dish versus main dish).