- cooking spray
 - 1 1/2 cups packed dark brown sugar
 - 1 cup butter, softened
 - 1/2 cup white sugar
 - 2 eggs
 - 2 teaspoons vanilla extract
 - 2 cups all-purpose flour
 - 1 1/2 teaspoons baking soda
 - 1 1/2 teaspoons salt
 - 3 cups old-fashioned rolled oats
 - 1 (11 ounce) package butterscotch chips
 - 16 chocolate sandwich cookies with extra creme filling (such as Double Stuf Oreo®)
 - flaked sea salt
 
- Line 2 baking sheets with parchment paper and spray with cooking spray.
 - Beat brown sugar, butter, and white sugar together in a bowl using an electric mixer until smooth and creamy, about 5 minutes. Scrape down sides of bowl a few times. Continue beating mixture while adding eggs, 1 at a time, beating well after each addition. Add vanilla extract and mix well.
 - Whisk flour, baking soda, and salt together in a separate bowl. Slowly add flour mixture to creamed butter mixture while beating on low speed until dough is just mixed. Fold oats and butterscotch chips into dough.
 - Scoop 32 balls of dough using a large cookie scoop and arrange on the prepared baking sheets. Spray the bottom of a broad, flat glass or bowl with cooking spray and press onto each dough ball to flatten. Place a chocolate sandwich cookie on top of 16 flattened dough balls and cover with remaining 16 flattened dough balls, sealing the edges together with your fingers.
 - Transfer stuffed cookies to a container or tray and cover with a lid or plastic wrap. Refrigerate at least 1 hour to overnight.
 - Preheat oven to 375 degrees F (190 degrees C). Line baking sheets with parchment paper.
 - Arrange cookies on the sheets with no more than 6 per sheet; top with a sprinkling of flaked salt.
 - Bake 1 tray at a time in the preheated oven until golden brown, 14 to 16 minutes. Cool on the baking sheet for 1 minute before transferring to a wire rack to cool.