Homemade Vanilla 13x9 Cake with Homemade Confetti Sprinkles

I used a new Martha Stewart recipe for a vanilla cake, frosting and homemade sprinkles for Livi's birthday cake. Since we missed Livi's family party at the Cruce's home, we planned a dinner and cake on Tuesday the 25th right after AA's piano lesson.
When Leaa said Livi's favorite cake flavor was vanilla I knew I had to up my game! With homemade vanilla extract and one vanilla bean in the batter, hoped for a delicious cake and it was! AA texted Livi to ask about her favorite color and it was blue or lavender; we went with three shades of purple sprinkles.
Making homemade sprinkles was so easy and looked just like the photo in the MS magazine. We used purple gel coloring and put some sprinkles in the cake batter. In order to put some in the batter, you need to make the sprinkles at least a day in advance to allow them to dry. The recipe says they will keep for a month! Ours were a little thicker, so next time will make smaller "lines".
I love this recipe and the sprinkles could be made in any color(s), think school colors, and on any size/style cake, just add them while the frosting is soft.

Making the sprinkles, should have a steadier hand but once broken up really doesn't matter. Making them thinner and even would be more "Martha Stewart"!

Cooking the milk frosting (flour and whole milk); it needs time to cool, so I made it in advance - beat in the butter and sugar right before serving the cake:

Recipes from Martha Stewart May 2017 magazine; I added one vanilla bean (scraping the inside):

Magazine page: