Mix sugar and corn syrup in heavy saucepan.
Set candy thermometer in place.
Stir and cook to 244F.
Add butter and warm cream slowly so mixture does not stop boiling.
Cook again to 244F, stirring gently.
Cool on wire rack to 220F.
Carefully stir in extract, then turn into 2 buttered 8-inch pans.
Set aside until firm enough to cut and wrap.