Walnut Maple Fudge

In a medium saucepan over medium heat, combine sugar, evaporated milk and butter. Bring to a boil and let roll 5 minutes. Remove from heat and quickly stir in marshmallows, white chocolate, chopped walnuts and maple flavoring. Spread in a 9x13 inch dish. Top with large walnut pieces, evenly spaced. Chill 8 hours or overnight. To serve, cut around large walnuts.