Line an 8-in. square pan with foil and grease the foil with 1 teaspoon butter; set aside. In a small heavy saucepan, combine the sugar, milk and remaining butter. Bring to a boil; cook for 5 minutes. Remove from the heat. Add butterscotch chips and graham cracker crumbs; stir until chips are melted.
Pour into prepared pan. Refrigerate until firm. Using foil, lift fudge out of pan. Discard foil; cut fudge into 1-in. squares. Store in an airtight container in the refrigerator.