Wash and dry watercress. Remove long stems. Heat a medium sized nonstick skillet on medium high. Add watercress and toss one minute until just wilted. Remove to a serving dish and sprinkle with salt and pepper to taste. Press pepper onto both sides of steak. Brown 2 minutes per sided. Remove to plate. Lower heat to medium, add shallots, garlic and mushrooms. Saute 5 minutes. Return steak and cook until done, 5 minutes for a 8 cm thick tenderloin. (3 minutes for thinner flank steak) Add brandy and cook 30 seconds. Remove steak and place on bed of watercress. Add cream to skillet and whisk. Add salt to taste. Spoon sauce over steak and serve with potatoes. Nutritional info per serving: 385 cal; 42g pro, 9g carb, 16g fat (38%)