Brown the bones and scraps of meat in the lard with the chopped onions, grated carrots, and the bouquet garni. Add the vinegar and let it evaporate before adding the flour. Sprinkle with flour and brown. Add the tomatoes, wine, stock and simmer at least 2 1/2 hours. Strain the sauce, squeezing the residue. Put back on the heat and cook until reduced to a syrup. Sear the medallions on a high heat with the butter, until rare. Keep them warm on a serving plate. Deglaze the pan with Cognac, add the raisins, peppercorns, pinenuts and the reduced sauce. Bring to a simmer and taste for seasoning. Off the heat add the cubes of butter, whisking all the time. Pour over the medallions. Serve with a sweet potato purÄe.
