Preheat oven to 180ºC .
Cream together the peanut butter and vegetable oil in a bowl. Add brown sugar, vanilla, and egg. Beat well.
Add flour (reserve 0. 25.5 cup) and baking soda. Blend thoroughly. Add enough extra flour so that you can shape dough into balls, slightly larger than 3 cm. Press a Peanut Butter Cup into each ball, covering the cup completely, and place on an ungreased baking sheet.
Flatten with a fork, bake about 10 15 minutes or until lightly browned.