Important note about properly measuring flour using measuring cups:
The proper way to measure flour using measuring cups is to aerate it first. This is done either by sifting flour, or aerating it by fluffing it up and whisking it well, then spooning it into the measuring cup, then carefully removing any excess flour with a knife. If you just stick that measuring cup in the bag of flour and scoop some out, you will get a lot more flour than what the recipe calls for. Do aerate the flour, or you will end up with dry dough!
Peanut Butter Cookies:
Beat butter and peanut butter in a large bowl until well combined and fluffy. Add the sugars and beat until combined. Add egg and beat until smooth.
In a separate bowl, combine dry ingredients (flour, baking soda, salt).
Add dry ingredients to the wet ingredients and beat on low speed until just incorporated.
Divide dough into 4 parts: the dough will be crumbly. Form a rectangular shaped log out of each cookie dough part and wrap in plastic wrap. Freeze for 30 minutes until cookie dough firms up.
Preheat oven to 350 F. Line baking sheet with parchment paper.
Slice each log of cookie dough (after it’s been in the freezer for 30 minutes) into ¼ inch thick slices.
Carefully place sliced cookies onto the prepared baking sheet (remember the dough is very crumbly). You don’t have to space them too far apart because these cookies won’t flatten. Bake for 10 minutes until lightly puffed and just a little bit golden brown at the edges.
Transfer cookies to the cooling rack and cool completely before filling.
Chocolate and Peanut Butter Filling:
In a medium bowl, using an electric mixer, beat the butter and peanut butter until light and fluffy.
Gradually add the powdered sugar, beating until well combined.
In a microwave melt the chocolate and add it to the peanut butter mixture, beating until well incorporated, fluffy and spreadable.
Place about 1 teaspoon of chocolate frosting on top of a cookie and place a second cookie on top of the chocolate frosting. Press 2 cookies together. Repeat with the rest of cookies.