|Preheat oven to 375ºF.
Combine flour, cornstarch, baking powder, and soda in bowl; stir well and set aside. Combine sugars, oil, and peanut butter in large bowl; beat until well blended. Add corn syrup, extracts and egg; beat well. Stir in flour mixture.
Shape dough into 1-inch balls. Dip tops in sugar, if desired, and place on baking sheet. With fork, flatten lightly in criss-cross fashion. Bake for 8 to 9 minutes or until lightly browned. Remove cookies from pan and cool on wire rack.
Makes 4 dozen, 1 per serving.