So I set out to make them. I realized that my new sprinkles (given their varying sizes, textures, and make-up (some have sixlets (chocolate-filled candies) in them) probably wouldn't mix into the bars well, so I used rainbow sprinkles for the bars themselves, and topped them with the fancy sprinkles. (And I had fun playing around with my macro lens for my iPhone and took these close-ups of the sprinkles!)
Basically, they're a glorified funfetti cookie base covered in vanilla buttercream (in fun colors!!) and then topped generously with beautiful sprinkles (I used a combination of 4 different kinds of sprinkles -- some regular rainbow sprinkles and 3 different pretty sprinkles mixes that I had bought [in even amounts, because I'm OCD], minus the few sixlets that I picked out and ate while I was making the icing.....but shhhh, no one else needs to know that!).
These really are gorgeous bars, and super tasty, too! I made sure to package up a bunch for B to bring to work this weekend, and some others for drinks I have dinner plans with for tomorrow evening.
from Cookies & Cups
For the bars:
1 cup butter, melted
1 1/2 cups granulated sugar
2 tsp vanilla
1/2 tsp kosher salt (I recommend crushing it between your fingers as you add it)
2 cups flour
1/2 cup sprinkles
For the frosting:
1 cup butter, room temperature
4 cups powdered sugar
2-3 Tbsp milk
Blue food coloring
Pink/red food coloring (I ended up using some pink and then a drop of purple to get a richer purple)
Sprinkles for garnish
Preheat the oven to 350F.
Line a 9 x 13" pan with foil, and coat the foil with nonstick spray
In a large bowl, whisk together the butter and sugar.
Add in the vanilla, eggs, and salt.
Whisk until smooth.
Using a rubber spatula, stir in the flour until just combined.
Finally, stir in the sprinkles.
Spread the batter into the prepared pan.
Bake for 25-30 minutes until the edges are set.
The bars might seem underdone, but allow them to cool completely.
Make the frosting.
In the bowl of a 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.
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 food coloring.
Mix until a pale blue color is reached and evenly mixed.
Remove half of the frosting and place in a piping bag. I chose not to use a piping tip on it, but you can use any tip that you'd like.
To the remaining frosting in the bowl, add 1-2 drops of pink/red food coloring or purple (if you have) and mix again until a pale purple/lavender color is reached and evenly mixed.
Add purple frosting to another piping bag.
Pipe or spread the frosting on top of the bars.
The original blogger piped rich swirls of frosting on the bars before cutting them I was afraid that it would get too messy, so I cut them and then piped a little dallop of either the blue or purple frosting on top.
Garnish with more sprinkles,
Note: If you pipe the frosting on the uncut bars, with glorious swirls as the original blogger did, you will need to double the amount of frosting. If you pipe it as I did, half the frosting recipe should be enough, but I'd make a full batch of frosting depending on how big you cut the bars (mine were quite small, about 1 x 1").