Coarsely chop the onion and garlic. Peel and dice the squash. Cut the cauliflower into 1-inch florets.
Heat a Tbspful of oil in a large pan, and gently sauté the onion for 5 minutes, add the garlic and the curry powder. Stir for a minute then add the squash and stir until they are well coated.
Add the cauliflower then the stock andcinnamon. Bring to a boil and cook for 20- 30 minutes, until tender.
Discard the cinnamon. Using a stick blender, process the soup until you get a smooth, velvety texture.
Taste and season with salt and pepper to your liking.
Serve with a dollop of yogurt (if you like) or some coriander leaves scattered on top and a slice of lemon on the side.