Chai roasted pumpkin soup with honey walnuts

Ingredients

• 1 pumpkin, peeled, chopped coarsely
• 1/2 ground cardamom
• 1/4 ground cinnamon
• 1/2 cracked black pepper
• olive-oil spray
• 1/4 (25g) walnuts
• 1 honey
• 1 small brown onion (80g), chopped coarsely
• 2 garlic, sliced
• 3/4 (180ml) salt-reduced vegetable stock
• 1 3/4 (430ml) water
• 1/3 (95g) low-fat greek yoghurt
• 2 roughly chopped fresh coriander leaves