For the cookie bars:
For the buttercream frosting:
- 1 c (2 sticks) unsalted butter, room temperature
- 3 c Better Batter Corn-Free Powdered Sugar
- 2-3 Tbl milk
- 1 tsp vanilla (I use clear vanilla, but regular vanilla extract will work too!)
- Additional candy sprinkles for garnish
Preheat and prepare.
Preheat the oven to 350 degrees. Line a 13x9 baking dish with parchment paper long enough to overhang the sides. These will be used as handles to pull out the cookie bars after baking. Lightly spray the parchment paper with cooking spray. Set aside.
Mix up the batter.
In a large bowl, combine the cupcake mix (reserving the sprinkles and powdered sugar for another recipe), flour, granulated sugar, baking soda, cream of tartar, salt. Whisk well to combine. Add the melted and cooled butter, eggs, and vanilla. Beat with an electric mixer on low speed for 1 minute or until the mixture is uniform and all dry ingredients have been incorporated. Stir in the candy sprinkles. Spoon the batter into the prepared pan and smooth into an even layer.
Bake the cookie dough for 30-35 minutes, rotating the pan halfway through baking. I tented my cookie bars with foil to prevent over browning about 20 minutes into baking. They are done when a toothpick inserted in the center comes out clean. Remove from the oven and transfer to a wire rack to cool completely.
Make the frosting.
In the bowl of a stand mixer or using a large bowl and an electric mixer, beat the softened butter, powdered sugar, and vanilla together until a thick consistency is reached. Add milk one tablespoon at a time until you reach a spreading consistency (this milk may be omitted if the consistency is already rather soft. This will depend on the temperature of the softened butter and your kitchen.) Spread the frosting on top of the cooled cookie bars. Add extra sprinkles to the frosting. Makes 20+ cookie bars.
Adapted from Betty Crocker