Melt the butter in a large saucepan

Fry the onion for 3 minutes

Add the chicken and half of the chicken stock to the pan

Bring to the boil

Reduce the heat

Simmer for 20 minutes

Let it cool

Process until smooth into a food processor or blender

Add the remainder of the stock

Season with salt and pepper

Add the chopped tarragon

Transfer the soup to individual serving bowls

Stir in the cream

Garnish the soup with fresh tarragon

Serve with deep-fried croutons