Preheat oven to 350 degrees F. Season steaks with salt and pepper, and then coat in flour. Heat oil in a skillet set over medium-high heat. Add steaks, brown on both sides, and then place in a casserole. Drain excess oil from skillet, and then add stock, garlic, rosemary and Worcestershire sauce. Bring to a boil, and then pour over steaks. Cover and bake until steaks are quite tender, about 75-90 minutes.
To make the potatoes, first gently boil until very tender. Drain, and then mash well. Whip in butter, buttermilk, and salt and pepper to taste.