Combine first 8 ingredients in a large saucepan or stockpot; bring to a boil; skim; lower heat and simmer for 1½ hours, skimming surface of stock from time to time. Strain stock; pour back into a clean saucepan and cook over a high heat, stirring from time to time, until strained stock is reduced to half the original quantity.
Make a roux with clarified butter and flour; cook until well blended; pour in strained stock and simmer, stirring from time to time, until sauce is cooked. Stir in double cream; correct seasoning and use as required. Makes