1. Line an 8-inch square baking pan with nonstick foil. Coat foil with nonstick cooking spray.
2. Combine syrup, sugar, heavy cream and salt in a medium-size saucepan. Bring to boiling over medium-high heat, stirring. Once boiling, cook 7 to 8 minutes or until mixture registers 238 degrees F on a candy thermometer.
3. Remove pan from heat; with an electric mixer, beat in butter and vanilla. Continue to beat on high power for 8 to 9 minutes, or until thickened, light in color, and fudge loses its glossy finish. Stir in nuts and spread into prepared pan. Let stand until firm, about 25 minutes. Cut into squares.