Step by step

Method

10 steps

1. 1

   Gather ingredients and preheat your oven to 350℉. Leave both sticks of butter out to reach room temperature. Grease a 9x13” baking dish with cooking spray or a little butter.

2. 2

   Combine 1 Tbsp rainbow sprinkles, sugar, baking powder, and flour in one bowl. Combine 2 tsp vanilla and egg in another smaller bowl.

3. 3

   Mix together dry ingredients in the first bowl and then add softened salted butter. Mix with a hand mixer until combined.

4. 4

   Then, add egg and vanilla mixture.

5. 5

   Once combined, pour in 1 cup milk and mix.

6. 6

   Pour batter into prepared baking dish and smooth it out so it’s level with a spatula.

7. 7

   Bake for 25-30 minutes until the edges are golden brown and a toothpick inserted in the center comes out clean. Let cool completely before frosting.

8. 8

   While your cookie bars are cooling, make frosting by combining softened unsalted butter, 1 tsp vanilla, powdered sugar, and 2 Tbsp whole milk with a hand mixer until smooth.

9. 9

   Frost the cooled cookie bars. I used an offset spatula.

10. 10

    Top with the remaining 1 tsp rainbow sprinkles. Slice and enjoy!