FILLING-- Place chocolate bar, peanut butter, sugar and salt in a medium bowl. Bring whipping cream to a light boil in a medium sauce pan. Pour whipping cream over chocolate mixture stirring well until smooth. Chill in refrigerator for 1 hour until thick and spreadable.
COOKIES--Using an electric mixer, cream butter and both sugars until blended. Add peanut butter mixing until creamy. Gradually beat in oil, vanilla then the egg.
In medium bowl, whisk, flour, baking soda, baking powder and salt. Gradually add to creamed mixture until just blended. Stir in chocolate chips.
Drop by teaspoonfuls onto cookie sheet. Bake for 12-15 minutes. Let sit a few minutes on cookie sheet before transferring to a cooling rack. Let cool completely.
ASSEMBLY--Spread 1 teaspoonful of filling onto flat side of cookie. Top with another cookie. Store in airtight container.