Peanut Butter Sandwich Cookies

Ingredients

• ½ cup plus 4 tablespoons unsalted butter, room temperature, divided (1 ½ sticks)
• 1 cup old-fashioned rolled oats
• 1 cup plus 2 tablespoons all-purpose flour
• 1 teaspoon baking soda
• 1 teaspoon salt
• ½ cup packed dark-brown sugar
• ⅓ cup granulated sugar
• ½ cup smooth peanut butter
• Turbinado sugar, for sprinkling

For the Peanut Butter Filling:

• ¾ cup peanut butter
• 4 tablespoons unsalted butter
• 1⁄4 cup confectioners' sugar
• ½ teaspoon salt

Instructions

1. 1
   Line a baking sheet with parchment paper; set aside. Melt 4 tablespoons butter in a medium saucepan over medium heat. Add oats and cook, stirring, until toasted, 5 to 10 minutes. Spread oat mixture onto prepared baking sheet and let cool.
2. 2
   Meanwhile, preheat oven to 350°. Line 2 baking sheets with parchment paper or a nonstick baking mat; set aside.
3. 3
   In a medium bowl, whisk together flour, baking soda, and salt; set aside. In bowl of an electric mixer fitted with the paddle attachment, cream together remaining 1/2 cup butter, brown sugar, and granulated sugar. Add peanut butter and mix until well combined.
4. 4
   Add oat mixture and flour mixture; mix on low speed until combined. Turn dough out onto a piece of parchment paper. Cover dough with a second piece of parchment paper and roll out dough, between parchment, to 1/4 inch thick. Carefully slide rolled dough onto baking sheet and transfer to refrigerator until chilled, about 20 minutes.
5. 5
   Remove top layer of parchment paper; cut out cookies using a 2-inch round cookie cutter. Place cookies 1 inch apart on prepared baking sheets; sprinkle with turbinado sugar.
6. 6
   Transfer baking sheets to oven and bake until golden, rotating baking sheets halfway through baking, about 10 minutes. Let cool completely on baking sheets.
7. 7
   When cookies have cooled completely, snip end of a pastry bag and squeeze peanut butter filling in a spiral motion on bottom side of half the cookies. Top with remaining cookies to form sandwiches.