In a saucepan bring 500ml water and 250ml orange juice to the boil. Add one pinch cardamom, one tsp salt, 1/4 white pepper and purple carrots. Cook until carrots are tender.
Transfer to a blender and purée until smooth. Add a little water if too thick. Keep warm. Repeat first three steps with orange carrots.
For orange caramel syrup, bring orange juice and sugar to the boil and reduce by half. Serve soups side by side, drizzled with syrup.