Spray the bottom of a heavy based saucepan with calorie controlled spray oil (or use olive oil in a spray bottle) - about 10 sprays.
Warm over a medium heat. Add the onions and saute for 4 or 5 minutes until they are starting to soften. If they start to stick to the bottom of the pan add a couple of tablespoons of water to unstick and continue stirring.
Add the garlic and ginger and heat for another 1 minute.
Add the ground coriander, cinnamon, curry powder, salt and ground cumin along with 1 tablespoon of water and heat, stirring continually for 2 minutes. If it starts to stick, add a little more water.
Add the stock and pumpkin and stir to combine. If you like a thinner soup you may like to add 1 - 1 ½ cup more water at this point.
Bring to the boil, then reduce the heat so that it gently simmers. Cover and leave to simmer for 10 - 15 minutes.
Remove from the heat and taste. Add more salt and pepper if needed. The addition of extra salt will be very dependant on the brand of chicken / vegetable stock that you use.
Puree the soup with an immersion blender or a stand blender.
Serve with a tablespoon of fat free natural yogurt and a sprinkling of crushed red pepper (optional).