Heat ½ dl (2 fl oz or ¼ U.S. cup) oil in a pan; add a Mirepoix comprising 100 g (3½ oz) carrots, 80 g (3 oz) onion, a few parsley stalks, a pinch of thyme, and half a crushed bayleaf and cook until lightly coloured. Moisten with 1 dl (3½ fl oz or ½ U.S. cup) vinegar, 2 dl (7 fl oz or ⅞ U.S. cup) of marinade and reduce by two-thirds. Add 1 litre (1¾ pt or 4½ U.S. cups) Sauce Espagnole and allow to simmer gently for 45 minutes. Ten minutes before passing the sauce, add 8 crushed peppercorns; pass through a sieve with a little pressure then add a further 2 dl (7 fl oz or ⅞ U.S. cup) of marinade. Bring to the boil, skim and carefully simmer for approximately 35 minutes so as to reduce the sauce to the required quantity.
Pass again through a fine strainer and finish with 50 g (2 oz) butter.
This sauce is suitable for serving with butcher’s meat which has been either marinated or not.