Melt 2 Tbsp (30mL) butter in skillet over medium-high heat.
Cook veal slices 4 to 5 minutes until golden brown, turning once. Remove from pan and keep warm.
Add remaining butter to skillet and cook mushrooms to golden brown. Add beef stock, bring to boil and simmer 2 to 3 minutes.
Add Marsala wine and return meat and any accumulated juices to the pan. Reheat 1 to 2 minutes.