I already had a recipe for the peanut butter buttercream that I wanted to use as the filling, so I just needed a recipe for the cookie part. I ended up finding one from The Kitchn and it worked out well! These cookies were moist and soft. These are actually like mini whoopie pies! If you are making a lot (for Christmas or a big party) I would double the recipe. I only got about 24 cookies out of this, but you might be able to make them smaller too and get a little more out of it. Also, the recipe I used was for cut-out cookies. I e-mailed the author of the post and asked if I could make them as drop cookies and she said it shouldn't be a problem. It wasn't. :) The only thing that changed was that I didn't have to chill the dough, which saved time!
These are a pretty simple and easy cookie to make, and they are easily customized too. You can make any type of flavored cream/filling that you want for the inside - peanut butter, caramel, nutella, peppermint (as in the original recipe), a fruit flavor. Anything you like! :)
Chocolate Peanut Butter Sandwich Cookies (a.k.a. Mini Whoopie Pies)
Source: The Kitchn
For the Cookies:
1/2 cup unsalted butter, softened
3/4 cup sugar
1 large egg
1 large egg yolk
1 teaspoon vanilla extract
1 1/3 cups all-purpose flour
1/2 cup dark cocoa powder
1 tablespoon ground espresso beans (optional)
1/2 teaspoon baking powder
1/2 teaspoon baking soda
1/2 teaspoon salt
For the Peanut Butter Buttercream Filling:
1/2 cup butter, softened
1 cup creamy peanut butter
3 tablespoons milk, or as needed
2 cups confectioners' sugar
For the Cookies:
Beat the butter, sugar, and vanilla in large bowl until light and fluffy. Add the egg and egg yolk and beat for 3 minutes. Add the flour, cocoa, ground espresso beans, baking powder, baking soda, and salt, and beat until there is no more visible flour and a soft, dark dough comes together. Scrape down the sides of the bowl and make sure the dough is fully mixed.
Heat the oven to 325°F.
Use a teaspoon to scoop out dough and roll into balls. Place them about an inch apart on the baking sheet. Gently press them down to flatten them into discs, but don't make them too thin. Bake the cookies for 5 to 8 minutes, depending on their size, or until no indentation remains when touched. When you remove the sheet from the oven, drop it onto a counter to get the cookies to flatten a little more. Let cool on the baking sheet for 10 minutes to firm up, then transfer to a wire rack. Let cool completely before making sandwiches.
While the cookies cool, make the buttercream. Place the butter and peanut butter into a medium bowl, and beat with an electric mixer. Gradually mix in the sugar, and when it starts to get thick, incorporate milk one tablespoon at a time until all of the sugar is mixed in and the frosting is thick and spreadable. Beat for at least 3 minutes for it to get good and fluffy. Note: I had to add a lot more milk than suggested.
Spread the buttercream onto half of the cookies; the amount you'll need will vary depending on the size of the cookies you make. Top with the remaining cookies and store in an airtight container.