Cut the stew meat into 1-inch cubes, removing any large pieces of fat. It's okay if there is marbled fat in the meat.

Season the beef with black pepper, garlic salt, and celery salt. Toss to coat. Sprinkle flour over the meat and toss again.

In a large skillet over medium-high heat, heat 3 tablespoons of olive oil. Brown the meat in batches for about 45 seconds on each side. Add more oil if needed. Transfer the browned meat to the slow cooker.

Reduce the heat to medium, melt 1 tablespoon of butter, and sauté the onions for 5 minutes. Add garlic and cook for an additional minute. Deglaze the pan with a splash of wine, scraping up any brown bits. Transfer this mixture to the slow cooker.

Add all remaining ingredients except for the peas, corn starch mixture, and 2 tablespoons of cold butter to the slow cooker.

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 potatoes are cooked through.

Add the peas during the last 15 minutes of cooking. Remove the bay leaves and rosemary stem.

Optional: To thicken the stew, combine ¼ cup of cold water with 3 tablespoons of cornstarch. Slowly add this mixture to the stew, stirring until thickened.

Turn off the heat and swirl in 2 tablespoons of cold butter for a smooth finish. This technique is called “Monter au Beurre”.