Start by prepping the ingredients. Dice onion, mince garlic, peel and chop carrots and slice potatoes. Season meat all over with salt, pepper, celery salt, and garlic powder.
Heat 1 tbsp neutral oil in a large pan over medium-high heat. Place seasoned meat in hot pan and don't touch for 4 minutes, ensuring a good sear. Flip over and sear for 4 more minutes. Carefully turn over on each side to ensure all sides of meat get seared then transfer to the slow cooker.
In the same pan, melt 2 tbsp butter over medium heat. Add diced onions and cook for 4 minutes. Add minced garlic and a splash of wine, scraping up any brown bits in the pan.
Transfer onion mixture to slow cooker. Add in carrots, potatoes, 1 cup wine, beef broth, tomato paste, beef bouillon, worcestershire, bay leaves, and rosemary sprigs. Cover with lid.
Cook on low setting for for 8 hours (begin checking at 7.5 hours). Meat should be fall apart tender and potatoes easily pierced with a fork.
Remove bay leaves and rosemary sprigs from pot. Shred meat using two forks or separate into small chunks if preferred. Add the frozen peas and let cook for 15 minutes.
Meanwhile, in a separate small bowl combine the cold water and cornstarch. Add mixture to slow cooker and stir well, this will thicken the stew. Add the last 2 tbsp cold butter and mix well.
Serve with toasted bread!