Preheat sauté pan (large enough to accommodate all 6 medallions without overlap) over medium high heat. Dredge each medallion in flour and shake off excess. Add butter to pan. When the butter is melted and begins to foam, add the medallions and sear on both sides. Remove to drain on paper toweling.
Drain the butter from pan and add shallots, cooking until translucent. Add the shiitake mushrooms, stirring to incorporate with shallots. Cook about 2 minutes. Remove pan from heat and add Cognac. Return to the heat carefully to avoid flare-up. Reduce Cognac until almost dry. Add veal stock and reduce by half. Season with salt and pepper. Add cream and reduce by half, stirring occasionally to blend flavors. Return medallions to pan and coat well with sauce. Place on plates and spoon sauce on top. Garnish with sprigs of fresh parsley.
Suggested wine - 2000 Mondavi/Frescobaldi Lucente or a favorite medium- to full-bodied red of your choice.