In a small bowl, cover the dried mushrooms with hot water. Let stand for 20 minutes. Rinse under warm running water and squeeze out the excess moisture. Chop mushrooms.
In large skillet, melt the butter over medium heat. Add the mushrooms, onion, drained green peppercorns and cracked black pepper. Cook, uncovered, over medium low heat for 15 minutes, stirring frequently.
Remove from heat. Add Marsala. Return to heat. Bring to boiling; reduce heat. Simmer, uncovered, 8 to 10 minutes or till wine is reduced by about half and mushroom mixture is slightly thickened, stirring occasionally.
Add whipping cream and condensed beef broth. Heat over medium heat till tiny bubbles just form around the edge; reduce heat. Cook over medium-low heat, stirring occasionally with a wooden spoon, for 20 to 25 minutes or till mixture thickens to desired consistency. Season to taste with salt; set aside.
Trim fat from steaks. For a charcoal grill, grill on the rack of an uncovered grill directly over medium coals to desired doneness, turning once halfway through. (Allow 14 to 18 minutes for medium rare and 18 to 22 minutes for medium.) For a gas grill, preheat grill. Reduce heat to medium. Place steaks on grill rack over heat. Grill as above.
To serve, reheat the Marsala Peppercorn Sauce; transfer to a serving bowl and pass with steaks. Serve with your favorite mashed potatoes.