1. Preheat the oven to 350°F. Line a 9×13 pan with foil and coat with nonstick spray. Set aside.
2. In a large bowl whisk together the butter and sugar. Add in the vanilla, eggs and salt and whisk until smooth. Using a rubber spatula stir in the flour until just combined. Finally stir in the sprinkles.
3. Spread the batter into the prepared pan.
4. Bake for 25-30 minutes until the edges are set. The bars might seen underdone, but allow them to cool completely.

Frosting

1. In the bowl of the stand mixer beat the butter for 1-2 minutes until it’s smooth. Turn the mixer to low and slowly add in the powdered sugar. Next add in 2 tablespoons of milk and mix on medium speed until it’s creamy, scraping the sides as necessary. If the frosting is too stiff add in 1 more tablespoon of milk until the desired consistency is reached. Finally add in 1-2 drops of blue fool coloring and mix until a pale blue color is reached and evenly mixed.
2. Pipe or spread the frosting on top of the bars.
3. Garnish with more sprinkles if desired.