Tender Slow Cooker Brisket
5 pounds flat-cut beef brisket, trimmed
2 tablespoons extra-virgin olive oil
4 large onions, thinly sliced
6 cloves garlic, minced
1 teaspoon dried thyme
1 teaspoon coarsely ground pepper
1 6-ounce can tomato paste
2 cups reduced-sodium beef broth
1 teaspoon salt
2 tablespoons butter, softened
2 tablespoons all-purpose flour
1 tablespoon Worcestershire sauce
Cut brisket into two or three pieces small enough to fit into a Dutch oven; pat dry. Heat 1 tablespoon oil in the Dutch oven over medium-high heat. Reduce the heat to medium and brown the brisket one piece at a time, about 2 minutes per side, adding an extra tablespoon of oil, if necessary, to prevent sticking. Transfer the brisket to a 5-quart (or larger) slow cooker.
Add the remaining 1 tablespoon oil to the pan. Add onions and cook, stirring occasionally, until softened, 3 to 6 minutes. Add garlic, thyme and pepper and cook, stirring, for 1 minute. Stir in tomato paste. Add beef broth and salt; bring to a boil.
Transfer the onion mixture to the slow cooker. Cover and cook until the brisket reaches desired tenderness (see Cooking tip), 4 to 5 hours on High or 8 to 10 hours on Low.
Transfer the brisket to a cutting board and slice or shred. Place in a serving dish; cover to keep warm. Transfer the gravy to a saucepan. Bring to a boil over medium-high heat and boil rapidly for 5 minutes to reduce slightly.
Meanwhile, mix butter and flour in a small bowl until smooth and creamy. Once the gravy has reduced, lower the heat to maintain a simmer. Stir in Worcestershire sauce. Whisk half the butter mixture into the gravy and return to a simmer. Cook, stirring, until it thickens slightly, 1 to 3 minutes. If the gravy does not thicken enough (it should have the consistency of a cream soup), add the rest of the butter mixture and repeat. Do not overcook. Serve the brisket with the gravy.
Cooking tip: Cook the brisket for the shorter amount of time suggested if you prefer firmer, sliceable meat. If you like it to be falling apart, for shredding rather than slicing, set your timer for the longer time.