loosely adapted from a recipe by Thomas Keller printed in the New York Times by Alice Q. Foodie
FOR THE COOKIE DOUGH:
3 cups all-purpose flour
2½ cups rolled or quick cooking oats
2 teaspoons baking powder
4 teaspoons baking soda
1/2 tsp sea salt
1 1/2 cups (3 sticks) butter, at room temperature
2/3 cup crunchy salted natural peanut butter
1 cup granulated sugar
1 cup firmly packed dark brown sugar
2 large eggs
1/4 cup blackstrap molasses
1½ teaspoons vanilla extract
1/2 cup coarsely chopped peanuts
FOR THE FILLING:
¼ pound (1 stick) butter, softened but still cool
½ cup salted crunchy or creamy all natural peanut butter
1 2/3 cups confectioners’ sugar
For cookie dough: preheat oven to 350 degrees. In a bowl, mix together the flour, oats, baking powder, and baking soda; set aside. Using a mixer with a paddle attachment, cream together the butter and peanut butter. Add sugars and beat at medium speed for 4 minutes, scraping down bowl twice.
Add the molasses and incorporate. On low speed, add eggs and vanilla. Add flour mixture and beat at low speed until well mixed, frequently scraping down bowl. Add peanuts and mix well.
Roll dough into balls about 1-1.5 inches in diameter and place on lined cookie sheets (a silpat is ideal). Wrap the bottom of a drinking glass in saran wrap, and flatten balls of dough to about 1/3 of an inch thick by pressing down with the bottom of the glass. Bake until cookies spread and are just dry on the top - about 8-10 minutes. Remove from oven and set aside to cool and firm up, 5 to 10 minutes. Transfer to a rack to cool completely before filling. The cooled cookies should be slightly flexible - if they are hard, bake the next batch one minute less. ( They'll still taste good - you just might want to eat them plain instead of filling them.)
For filling: using an electric mixer, cream together the butter, peanut butter and confectioners’ sugar until very smooth. Add more sugar if it seems to be too soft - or place in the refrigerator to firm up.
To assemble cookies, use a spatula to spread a layer of filling on the underside of a cookie and sandwich the cookies together.