Preparation:
Spray a large saucepan with oil and heat. Cook onion over medium heat for 3-4 minutes, until soft. Add garlic, chilli and ground coriander, cook, stirring, for 1 minute. Add sweet potato and chicken or vegetable stock. Bring to the boil, then reduce heat and simmer, partially covered, for 20 minutes, until sweet potato is tender. Cool slightly and purée in a blender until smooth. Return to the saucepan, add milk and reheat gently. Stir through coriander and garnish with extra whole leaves if desired. Serving suggestion: Slice the top off the cobs. Scoop out chunks of bread from the inside to make a well, but leave a small amount attached to the crust. Bake cobs in a preheated 210°C (415°F) oven for 5-7 minutes until the crust is crisp. Place cobs on serving plates, ladle soup into them, and sprinkle with fresh coriander. Arrange cob "lid" and bread chunks around the cob as soft croutons. Eat the cob "bowl" after the soup. Serve with salad.