Step 1

Season the beef pieces on all sides with salt and pepper. Heat the oil over medium heat in a skillet until hot and rippling. Add some of the beef in a single layer, not touching, and cook for 30 seconds or so until golden, flip and brown on the other side. Transfer beef to the insert of 6-quart slow cooker. Repeat with remaining beef, adding additional oil, if needed (let it heat up before adding more beef pieces).

Step 2

Once the beef has all been browned and transferred to the slow cooker, add the onions to the skillet set over medium heat. If the skillet is dry, add a teaspoon or so of oil.

Step 3

Cook the onions for 3-4 minutes, until translucent. Scrape up any browned bits from the bottom of the skillet. Add the garlic and cook for another minute. Pour in the beef broth or stock and Worcestershire sauce and bring to a simmer, scraping up bottom of pan.

Step 4

Pour mixture into the slow cooker with the beef. Add the bay leaves and thyme. Cover and cook on low for 8-9 hours or 4-5 hours on high until beef is tender.

Step 5

Transfer the beef to a dish and cover to keep warm. At this point you can strain the liquid in the slow cooker to remove any solids/onions or use as is for the gravy. You should have about 3-4 cups of liquid.

Step 6

For the gravy, in a medium saucepan over medium heat, melt the butter. add the flour and whisk to combine. Cook, stirring constantly, for 1-2 minutes until bubbling (it's ok if it browns slightly). Add the reserved liquid from the slow cooker about one cup at a time, whisking vigorously to avoid lumps.

Step 7

Bring the mixture to a simmer and cook, stirring constantly, until thickened. Stir in the red wine vinegar and season to taste with additional salt and pepper, to taste. If the mixture is too thin, stir together equal parts softened butter and flour until smooth and quickly whisk into simmering gravy. If the mixture is too thick, thin with additional beef broth.

Step 8

Add the beef pieces back to the slow cooker or to a serving dish and pour the gravy over the top. Serve over mashed potatoes with fresh parsley (optional).