Preheat the oven to 300 degrees F. Season meat with salt and pepper and sear on all sides in a hot saute pan. Place meat in a large roasting pan and cover with thyme, garlic, onions, carrots, chicken stock, and potatoes. Braise in the oven for 2 hours or until meat is tender. Strain liquid and place in an ice bath. Cool meat in liquid. Chop roasted onions and potatoes into a small dice. Shred beef and mix with potatoes, onions, chives, and parsley. Raise the oven to 350 degrees F. Heat a 10-inch cast iron skillet and add 1 tablespoon of butter. Place 2 cups of roast beef mix in skillet and place in the oven for approximately 15 minutes or until meat is slightly crisp on outside. Serve with poached eggs and hollandaise sauce, if desired.