Rub salt and ground black pepper over both sides of the steak.
Heat a dry saute pan over high heat. When pan becomes very hot add butter, let melt, then add steaks. Turn steaks only once, and cook to desired degree of doneness (approximately 3 minutes per side for medium-rare, depending on exact thickness.)
Add the Cognac to the pan, let sit for 5 seconds, and then light a match to it. Flame should burn out after approximately 10 seconds. (If flame continues to burn, put it out by placing a lid on the pan).
Remove steak from pan, leaving the drippings in the pan, and reserve on a warm plate and cover with aluminum foil.
Reduce heat to low and slowly stir Dijon and half-and-half into the drippings. Add peppercorns. Stir and simmer for a couple of minutes until sauce becomes thick. Place steaks on warmed serving plates. Pour sauce over steak.