This recipe is great. It's quick, tasty, and you can substitute pumpkin or carrot for the sweet potato. You can also vary the flavour by experimenting with different stocks, different curry pastes or replacing the coconut milk.
It freezes well, too.
Spicy sweet potato soup
2 Tablespoons Curry paste of your choice (I used green this week)
1 kg sweet potato (or carrots, or pumpkin - parsnip maybe?)
1 L stock
1 can coconut milk (optional, or easily replaced by evaporated milk, normal milk or cream)
Heat the currypaste until fragrant, in a large saucepan. Add the stock and the sweet potato, and boil until the sweet potato is tender. Take the soup off the heat, and blenderise it until smooth (I use a hand blender in the pot, but whatever works). Add the coconut milk and heat through.