Preheat oven to 180oC (160oC fan-forced). Toss carrots with the oil, spices and sugar. Spread onto a lined oven tray and cook for 35 minutes until tender.
Heat oil in a deep saucepan. Add onion, garlic, ginger and mustard seeds. Cook for 3-4 minutes until onion is tender and seeds are popping. Add carrots to the pan with the stock, water and 1/2 cup of the SuperBlend. Bring to the boil and simmer for 10 minutes until the blend is tender. Using a hand-held blender, puree until smooth.
Add remaining blend to the soup and cook for a further 10 to 12 minutes. Season to taste and serve with a dollop of yoghurt and chopped chillies.