Peel then dice the sweet potatoes. Scatter them onto a baking tray. Dust with cinnamon, drizzle with oil then season with salt and pepper. Bake in a medium hot oven for 20-25 minutes until soft and golden.
Ffinely chop the onion and garlic. Roughly chop the broccoli.
Heat a Tbsp of olive oil in a saucepan then gently sauté the onion and garlic for about 5 minutes, until soft. Add the curry powder, stir for a minute.
Add the broccoli, put the lid on for a couple of minutes, then pour over the stock. Cook for about 10-15 minutes, until the broccoli is tender.
Add the sweet potatoes to the soup and the fresh herbs. Process in liquidiser or with a stick blender until you get a velvety soup. Reheat if necessary.