Sweat the diced onion in the butter until soft and translucent.
Add the sliced carrots to the pan and cook, stirring from time to time, for a further 5 minutes.
Add the garlic and the washed and chopped stems of the coriander. Pour over the chicken stock, season with salt and pepper and the sugar, and bring to the boil. Lower the heat and simmer for 30 minutes.
Put the c