Cake Mix Sandwich Cookies with Strawberry Buttercream

No one will believe that these impressive (but effortless) spring treats start with a packaged cake mix. The strawberry cream filling for this sandwich cookie uses both fresh and freeze-dried berries to give it a powerful, rich strawberry flavor. While it's the perfect addition to these puffy vanilla cake mix brownies, you'll probably come back to the recipe again and again for icing puff cakes and cupcakes. Freeze-dried strawberries can be found in many grocery stores and online. Pro tip: Don't skip cooling the dough; this allows the coconut oil to solidify and helps the liver keep its shape during baking.
Prepare the cookies: Preheat the oven to 350 ° F. Line 2 lined baking sheets with parchment paper. Combine the cake mix, eggs, butter, freeze-dried strawberries, and baking powder in a large bowl.Form the dough into 30 balls (1 1/2 inches thick); place on prepared baking sheets about 2 inches apart. Freeze for 10 minutes.Bake in the preheated oven until golden brown, about 9 minutes. Transfer the baking sheets to a wire rack; let the cookies cool on the baking sheets for 5 minutes. Transfer the cookies directly to a wire rack; let cool completely, about 30 minutes.Prepare the frosting: Chop the strawberries in a food processor or blender until smooth. Set aside.Beat the butter using a heavy-duty mixer with a paddle attachment on medium speed until creamy, about 1 minute. Gradually add the powdered sugar until smooth. Add the vanilla, salt and mashed strawberries, and beat on medium speed until the mixture is creamy, about 1 minute. Increase speed to medium-high; beat until the dough is light and fluffy, about 1 minute. Add the crushed freeze-dried strawberries.Transfer the icing to a pastry bag with a star-shaped tip. Spread the strawberry frosting over 15 chilled vanilla cookies; top with the remaining cookies. Garnish with chopped freeze-dried strawberries.