For the cookies: In a large bowl or stand mixer set to low, combine softened butter, peanut butter, sugar, brown sugar, vanilla, and egg. Beat well until everything is combined. In a separate dry bowl, add flour, salt, baking soda, and baking powder. Mix until combined. Add your dry mixture a little at a time to your wet mixture until everything is combined evenly. Next, fold in the oats. Roll your cookies into 1-2 tablespoon balls and place on a cookie sheet lined with parchment paper. Push your cookies down with a fork until they are about 1/4 inch thick. (If the fork is sticking, coat with a little water or oil). Bake in an oven set to 350 degrees Fahrenheit for about 10-13 minutes. Once done, set on a cookie rack to cool. While cookies are cooling, prepare your filling.
For the optional cookie filling: In a mixer or large bowl, cream together butter, powdered sugar, and peanut butter. The consistency should be like the filling of an Oreo. Once cookies are cool, spread your filling on the bottom side of one cookie and top with another cookie, making a sandwich. Enjoy!
