1-Prepare the Meat: Cut the meat into 1-inch cubes, removing large fat pieces but retaining marbled fat. Season the beef with black pepper, garlic salt, and celery salt, then coat with flour.

2-Sear the Beef: Heat olive oil in a skillet over medium-high heat and sear the beef in batches for about 45 seconds per side. This step builds a rich flavor base. Transfer the seared beef to the slow cooker.

3-Soften Aromatics: Melt 1 tablespoon butter in the skillet over medium heat. Soften onions for 5 minutes, add garlic for 1 minute, and add a splash of wine to scrape up the browned bits from the bottom. Transfer this onion mixture to the slow cooker.

4-Combine Ingredients: Add beef broth, bouillon cubes, Worcestershire sauce, tomato paste, carrots, potatoes, bay leaves, rosemary, and remaining ingredients to the slow cooker. Do not add the peas, corn starch mixture, or the remaining butter yet.

5-Slow Cook: Cook on low for 7 ½ to 8 hours or on high for 3 ½ to 4 hours until the vegetables are tender and the beef is fork-tender.

6-Finish and Serve: Add peas during the last 15 minutes of cooking. Remove bay leaves and rosemary stem before serving. If desired, thicken the stew by stirring in a mixture of ¼ cup cold water and 3 tablespoons corn starch. Finally, turn off the heat and swirl in the remaining 2 tablespoons cold butter to create a smooth, velvety finish.