- Preheat oven to 350°F.
- With a thin, sharp knife, make slits in the meat and insert the slivers of garlic. Place the meat in a dish, spread crushed garlic and 1 sliced onion over the meat, and pour on the vinegar. Marinate for 6 hours at room temperature or overnight in the refrigerator, turning several times.
- Heat bacon drippings in a deep, heavy skillet large enough to hold the brisket. Remove the brisket from the marinade and discard the onion and vinegar. Dry with paper towels. Brown the meat well on each side. Remove brisket to a platter.
- In the fat remaining in the skillet, sauté the remaining onions until deeply browned. Pour in 1/2 cup coffee. Bring to a boil, stirring and scraping the bottom of the skillet to loosen the browned bits.
- Spread the onions and liquid from the skillet in a shallow baking dish. Place the brisket on the onions. Sprinkle liberally with salt and freshly ground pepper. Pour in the remaining coffee and water. Cover tightly with heavy-duty aluminum foil and place in oven.
- Roast at 350°F for 30 minutes. Reduce oven temperature to 250°F and roast for an additional 4 hours or until meat is very tender.
- Let brisket rest for at least 20 minutes before slicing. Slice the brisket across the grain. Skim the fat from the pan liquid, and return the meat slices to the pan.
- Makes 6 to 8 servings, depending upon appetites.