Heat your oven to 220°C/Fan 200°C/Gas 7. Put a large roasting dish on the top shelf to heat up.
Peel or scrub your carrots. Cut into 2-3 cm chunks. Tumble into the warmed roasting dish. Season well. Gloss with 1 tbsp oil. Roast for 15 mins. Halve, peel and finely chop your onion. Add it to the carrots after 15 mins. Roast for a further 10 mins or till everything’s tender.
Peel and finely chop your garlic. Fold into the cooked carrots. Set aside for the garlic to cook in the residual heat.
Roughly chop the fresh coriander. Save a pinch for garnish. Add the rest to a food processor or blender. Add the warm carrot mix and 500 ml stock (homemade or made up with your stock cube). Blend till smooth. Add more stock or water if needed to reach the desired consistency. Season to taste.
Set a frying pan over a high heat. Add 1 tsp of the coriander seeds. Toast till just fragrant. Garnish the soup with the coriander seeds and the reserved fresh coriander.