Preheat oven to 350 degrees
Cream together softened butter, peanut butter, white and brown sugars, and vanilla
Add the egg and mix thoroughly
Add the flour, baking powder, salt, and baking soda together and then pour in the creamed mixture and mix thoroughly
Add the oatmeal and mix
Use a teaspoon to measure out dough and place on greased cookie sheet
Place 12 cookies on a sheet and used fork to lightly flatten, leaving the traditional peanut butter markings on cookie.
Bake in oven for 10-12 minutes and let cool on wire rack
Cream together butter, confectioners sugar, peanut butter, and heavy cream
Sit aside until cookies are baked and cooled
Once cookies are cooled, use a knife to spread filling on bottom side of one cooking, then press the bottom of another cookie onto the filling... making a sandwich
The cookies would be great without filling and the filling could go on a single cookie instead of making a sandwich.