Cream of celery soup

celery soup (1 of 1)1 bunch of celery
1 tablespoon butter
1 large onion
3 cloves garlic
3 sprigs thyme
1 tablespoon tarragon
3 tablespoons flour
1 litre vegetable or chicken stock
200 ml cream
salt and pepper

Remove the leaves from the celery stalk and chop the stalks into 2 cm pieces. Peel and dice the onion, crush the garlic and take the thyme leaves of the stems. In a large heavy based pot cook the celery, onion, garlic and thyme leaves in the butter until soft then add the flour and cook for 2 minutes, add the stock and tarragon and simmer  for 20 minutes or until the celery is cooked and soft. Blend well until smooth add the cream and bring back to the boil season with the salt and pepper and serve.