Prepare the beef: Shake the beef stew meat in a resealable plastic bag with the flour and seasoning salt until evenly coated.
Heat olive oil in a skillet: Add the floured stew meat to the pan and brown on all sides. Remove using a slotted spoon or tongs and place into the bottom of a slow cooker. Season with pepper.
Sauté the onion: In the same hot skillet, sauté the diced onion for 2 minutes. Don’t worry about cleaning it out in between – that’s added flavor! Transfer the onions into the slow cooker as well.
Make the broth mixture: Pour the Worcestershire sauce, water, and beef demi-glace (or Swanson Flavor Boost) into the skillet and whisk until mixed, making sure you scrape up any browned bits in the bottom of the pan. Turn off the heat and set aside.
Combine ingredients in the slow cooker: Add the diced potatoes, carrots, celery, and bay leaves to the slow cooker. Pour the broth/Worcestershire mixture into the slow cooker as well.
Cook: Cover and cook on low for 8 hours.
Serve: Remove the bay leaves before serving. Enjoy your hearty and comforting beef stew!
