Preheat oven to 200°C. Line a large oven tray with baking paper.
Place pumpkin on tray, in a single layer; sprinkle with cardamom, cinnamon and pepper, spray with oil. Roast for 25 minutes or until tender.
Meanwhile, line a small oven tray with baking paper. Place nuts on tray, drizzle with honey. Roast for 5 minutes or until golden. Cool.
Heat rice bran oil in a large saucepan over medium heat. Cook onion and garlic, stirring, for 5 minutes or until softened. Add pumpkin, stock and the water to the pan; bring to the boil. Remove from heat; cool for 10 minutes.
Blend or process pumpkin mixture until smooth. Return pan to heat, stir until hot. To serve, drizzle soup with yoghurt; sprinkle with nuts and coriander.