Preheat the oven to 200C
Peel and slice the carrots into ½ inch rounds, place them on a flat baking tray and sprinkle with 1 tbsp of the olive oil and a good pinch of salt.
Roast for 15 to 20 minutes until soft and slightly brown.
Place the vegetable stock in a large saucepan with the peeled ginger and the sprig of rosemary, bring to the boil and simmer gently for 15 minutes.
In another saucepan sauté the chopped onion in the remaining olive oil until lightly brown and soft.
Add the crushed garlic and roasted carrots.
Remove the ginger and the rosemary from the stock and pour over the onions and carrots.
Bring to the boil and then simmer gently until the carrots are very soft.
Leave to cool slightly and then puree the mixture until completely smooth, adding a little more stock if the soup seems too thick.
Season with salt and freshly ground black pepper to taste.
To serve, reheat the soup gently and serve garnished with a little swirl of crème fraiche and some finely chopped chives.