Line an 8-in. square pan with foil; grease the foil with 1 teaspoon butter and set aside., In a large heavy saucepan, combine sugar, corn syrup and remaining 1 cup butter; bring to a boil over medium heat, stirring constantly. Boil slowly for 4 minutes without stirring., Remove from the heat; stir in milk. Reduce heat to medium-low and cook until a candy thermometer reads 238° (soft-ball stage), stirring constantly. Remove from the heat; stir in vanilla., Pour into prepared pan (do not scrape saucepan). Cool. Using foil, lift candy out of pan. Discard foil; cut candy into 1-in. squares. Wrap individually in waxed paper; twist ends.