Prepare an 8x8x2-inch pan by lining it with aluminum foil, extending the foil over the edges of pan. Spray the foil with nonstick cooking spray.
Combine sugar, marshmallow crème, evaporated milk and butter in heavy 3-quart saucepan. Cook over medium heat, stirring constantly, until mixture comes to full boil, Once it boils, stir continuously for five minutes.
Remove pan from heat; immediately stir in butterscotch chips, stirring until chips are melted and smooth. Stir in nuts and vanilla. Pour into prepared pan.
Allow the fudge to set at room temperature for two hours, or in the refrigerator for one hour. Once set, lift it from the pan using the foil as handles. Cut the fudge into small squares. Store tightly covered in refrigerator.