Coarsely crush peppercorns in mortar with pestle. Season steaks with salt. Sprinkle peppercorns over both sides of steaks, pressing to adhere. Heat oil in heavy large skillet over medium-high heat. Add steaks and cook to desired doneness, about 3 minutes per side for medium-rare.
Meanwhile, heat bourbon in heavy small saucepan over medium heat until warm. Remove from heat; carefully ignite with match. Let burn 30 seconds, then cover to extinguish flame.
Transfer steaks to plates; tent with foil to keep warm. Add 1 tablespoon butter and shallots to drippings in skillet; sauté 2 minutes. Add stock and bourbon; boil until reduced by half, about 3 minutes. Remove from heat. Add remaining 5 tablespoons butter, 1 tablespoon at a time, whisking just until melted. Spoon sauce over steaks and serve.