Preheat oven to 325.
Line 2 cookie sheets with heavy-duty foil.
Spray cooking oil over the top of the foil.
In a heavy saucepan, combine corn syrup, sugar, and butter.
Cook over medium heat, stirring constantly, until mixture comes to a boil.
Remove from heat; stir in flour and walnuts until well blended.
Add vanilla and mix well.
Drop by teaspoonful, 3 inches apart, onto foil-lined cookie sheets.
Bake 8 to 10 minutes.
Cool thoroughly on foil; peel off wafer.
Dip half of the wafer into melted chocolate.