Cut the turbot bones into pieces and disgorge.
Roast the bones in some butter in a copper frying pan.
Make sure to separate bits that stick to the bottom of the pan.
Once the bones are nicely roasted, add the garnish of sliced vegetables and herbs. Allow to simmer.
Add the concentrated veal stock and cook over low heat for 30 minutes.
Strain through a fine sieve using a muslin cloth.
Reduce by half. Mix with butter.