Line an 8-inch square baking pan with plastic wrap; set aside.
In a large microwave-safe bowl, mix corn syrup and evaporated milk until blended. Microwave for 3 minutes on high. Remove from microwave and stir in chocolate chips until melted. Stir in powdered sugar and beat for 2 minutes until well incorporated. Stir in nuts, if using.
Spread fudge evenly in lined baking pan. Cover with plastic wrap and chill three hours until firm. Cut into squares and serve.