Sprinkle the remaining packet of dry onion soup mix evenly over the top of the brisket, pressing it lightly so it adheres to the surface.Pour the beef broth around (not directly over) the brisket, so you don’t wash off the soup mix. The liquid should come up the sides of the meat slightly but not cover it.Cover the slow cooker with the lid and cook on LOW for 8 to 10 hours, or until the brisket is very tender and can be pulled apart easily with a fork. Avoid lifting the lid during the first several hours, as this releases heat and can lengthen cooking time.
Once the brisket is tender, carefully transfer it to a cutting board, tent loosely with foil, and let it rest for 10 to 15 minutes. This rest helps the juices redistribute, so the slices stay moist.While the meat rests, stir the onions and cooking juices in the slow cooker. The onions should be soft and translucent, and the liquid should be a rich, dark brown gravy. If you’d like it a bit thicker, remove the lid and cook on HIGH for 15 to 20 minutes to reduce slightly.Slice the brisket across the grain into thick slices. Arrange the slices on a warm white serving platter or dinner plates.
Spoon the caramelized onions and plenty of the dark, savory pan juices over the sliced brisket. Serve hot, with extra onion gravy on the side for spooning over your chosen starch.
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