Melt butter in a heavy 3-quart saucepan over medium heat. Add sugar and corn syrup, and cook, stirring constantly, 6 to 8 minutes or until mixture turns a deep caramel color. Gradually add cream, and cook, stirring constantly, 1 to 2 minutes or until smooth. Remove from heat, and let cool. Chill 2 hours or until thickened and spreading consistency.
Note: Caramel Filling may be made up to 3 days ahead and refrigerated. Let stand at room temperature 1 hour or until spreading consistency.