Season the beef cubes with salt and pepper. In a large skillet, heat olive oil over medium-high heat. Brown the beef in batches for about 5 minutes until caramelized on all sides. Transfer the beef to the slow cooker when done.
In the same skillet, add the chopped onion and garlic. Sauté for about 2-3 minutes until fragrant and translucent. Transfer them to the slow cooker.
Add the sliced carrots and cubed potatoes to the slow cooker on top of the beef and onions.
In a separate bowl, whisk together the beef broth, tomato paste, Worcestershire sauce, thyme, rosemary, and bay leaf. Pour this mixture over the beef and vegetables in the slow cooker.
Set the slow cooker to low and cook for 8 hours or high for 4-5 hours, until the beef is tender and the vegetables are cooked through.
About 30 minutes before serving, add the frozen peas to the slow cooker and stir gently.
Remove the bay leaf. Taste and adjust seasoning if necessary. Serve hot, garnished with fresh parsley if desired.