Preheat the oven to 350 degrees F.

Bring a large pot of salted water to a boil over medium heat. Add the potatoes, reduce the heat and simmer until the potatoes are cooked through and tender. Drain, return to pot and mash with a potato masher.

In a small pot over low heat, add the butter and milk and heat until hot. Mix the butter and milk mixture to the mashed potatoes and season with salt and pepper, to taste. (For very creamy potatoes use a hand mixer to incorporate the milk and butter mixture. Only mix for about 45 seconds to prevent potatoes from getting gummy.) Set aside.

Evenly divide the beef stew into 4 (11-ounce) ramekins. Top with the mashed potatoes and bake until the stew is bubbling and potatoes are slightly browned on top, about 30 minutes.

In a 6-quart slow cooker combine the celery, carrots, potatoes, onions, thyme and beef. In a large bowl, stir together all the remaining ingredients and pour over the beef and vegetables in the slow cooker. Cover and cook on high for 5 hours. Transfer to a serving bowl and serve with Beer Biscuits.