Add the tomato paste and cook for another 2-3 minutes. Add the cider vinegar, dark brown sugar, Dijon mustard, and Worcestershire sauce, stirring to scrape up all of the bits on the bottom of the pot.
Add 1 quart of the chicken stock and the ham hock and bring up to a simmer. Add the browned brisket to the pot and nestle it and the ham hock down into the liquids. Bring the pot back up to a simmer, place a lid on it and transfer to the oven. Braise for 3 hours or until the brisket is fork tender. To check if it is tender, remove the pot from the oven and stick the brisket with a fork at its thickest part. If the fork easily slips out, the brisket is tender and ready. If not, return it to the oven for another 20 minutes and check it again. Once it is tender and out of the oven, let it rest in the pot with all the liquids for about 15 minutes. Remove the brisket to a cutting board. Remove and discard the ham hock form the pot. Let the sauce remain in the pot until ready to serve.
Combine remaining 1 quart plus 2 cups of chicken stock, the milk and honey in a large sauce pot over high heat and bring up to a boil. Once bubbling, turn the heat down to medium and pour the polenta in a slow steady stream while whisking it continuously. Continue to cook and stir until the polenta is thick, 2-3 minutes, drop in the butter and set aside until ready to serve.
Slice the brisket into slices about 1/4-inch thick with a long, thin, sharp knife against the grain of the meat. Serve a few slices of brisket topped with the sauce over the polenta, sprinkle with the parsley and toasted, chopped pecans.