No one will believe these impressive (yet low-effort) spring treats start with a boxed cake mix. The strawberry buttercream filling for these sandwich cookies uses both fresh and freeze-dried berries in order to deliver a potent punch of vibrant strawberry flavor. While it’s the perfect accompaniment to these pillowy vanilla cake mix cookies, you’ll likely find yourself returning to the recipe again and again for icing layer cakes and cupcakes. Freeze dried strawberries can be found at many grocery stores and online. Pro tip: Don’t skip chilling the dough; this allows the coconut oil to solidify and helps the cookies maintain their shape while baking.