1. Heat a medium-sized saucepan over medium-low heat and add the oil. When the oil is hot, add the onion, garlic, gingerroot, and curry powder. Cook, partially covered, for about 7 minutes, or until the vegetables begin to soften.
2. Add 1 cup of the stock, the potato, and the broccoli stems (not the florets), and bring to a boil.
3. Reduce the heat to low, cover, and cook for about 15 minutes, or until broccoli stems and potato are tender.
4. Add the broccoli florets, 1/2 cup of the stock, cover, and cook for about 10 minutes, or until the florets are tender.
5. Place the remaining 4 to 4 1/2 cups of chicken or vegetable stock in a separate pot and bring to a boil over high heat.
6. Put all the vegetable ingredients in a food processor fitted with a steel blade and gradually add the boiling chicken stock. If necessary, this can be done in 2 batches. Add salt and pepper to taste.