Chilled carrot and orange soup

• 1 lb (450 g) new carrots
• 1 onion
• 1

Scrape and thinly slice the carrots. Peel and finely chop the onion. Melt the butter in a large saucepan over low heat, add the carrots and onion, cover with a pan lid, and cook gently for 5 minutes to soften the onion but not brown.

Pour the stock into the pan, add the sugar and season with salt and pepper. Bring to the boil, then lower the heat and cook gently, covered, for 40 minutes