Peel off the bacon rind, finely dice the bacon and leave it over a low heat until the bacon has liquefied. Now add the oxtail pieces and braise with port wine, beef broth, thyme, garlic cloves and tomato puree, covered, in a preheated oven at 160 °C for about 4 hours, until the meat can be effortlessly removed from the bones with just finger pressure. Discard the bones and shred the meat with a very sharp knife or in a cutter so that the individual meat fibers are still clearly noticeable and no mush is formed. Mix back into the roasting residue, stir, and bring back to a boil. Season to taste with salt, pepper and herbs. Allow to cool slightly and fill into jars while still warm.