3/4 c. all-purpose flour
1/2 tsp. baking soda
1/4 tsp. baking powder
1/2 tsp. salt
8 Tbl. (1 stick) unsalted butter, room temp.
1/2 c. creamy peanut butter
1/2 c. sugar
1/2 c. light brown sugar, packed
1 large egg
1 tsp. vanilla
1 c. quick-cooking oats
Filling:
4 1/2 Tbl. unsalted butter, room temp.
1/2 - 3/4 c. creamy peanut butter
1 1/2 c. powdered sugar
pinch of salt
1 tsp. vanilla
1-2 Tbl. milk
Preheat oven to 350 degrees. Whisk together flour, baking soda, baking powder and salt; set aside. In large bowl, cream together butter, peanut butter, sugar and brown sugar until light and fluffy, about 4 minutes. Scrape bowl. Add the egg and vanilla. Add the dry ingredients and beat until just combined. Add the oats and beat just enough to distribute evenly. Using a small ice cream scoop, drop dough onto cookie sheet, leaving 2-inches between each. Bake for 10-12 minutes or until golden and puffed. (I baked mine 11 minutes and I got 26 cookies, making 13 sandwiches. They will look under-done, but they will set up). Cool completely and place a spoonful of filling on half of the cookies and top with the other half to form a sandwich.
Filling: Beat butter and peanut butter until fluffy. Add powdered sugar and beat until combined. Add pinch of salt, vanilla and 1 Tbl. of milk. Beat until smooth and fluffy. If it is too thick, add another Tbl. of milk.