Funfetti Cake

1. Preheat the oven to 350F and grease a 9×13 baking dish. Line with a sheet of parchment paper, covering the bottom and two longest sides with some overhang for easy removal. 
2. In a large bowl using a hand or stand mixer with the paddle attachment, mix the butter and sugar on medium-high speed for 1 minute until light and fluffy. 
3. Then scrape down the bowl and mix in the oil on medium speed to create a creamy consistency. 
4. Mix in the vanilla and eggs until smooth. 
5. Scrape down the bowl, then add in the cornstarch, baking powder, and salt and mix to fully incorporate. 
6. Scrape down the bowl and mix in the water until smooth. Then mix in all of the flour on low speed and about halfway through mixing, pour in the buttermilk and mix until the batter is thick but smooth. Scrape down the bowl and mix again to ensure everything at the bottom is well incorporated, then fold in the sprinkles.
7. Spread the batter in the pan and bake for 32 to 38 minutes or until the cake is evenly puffed and a toothpick inserted comes out clean with a few moist crumbs. Allow to cool for 20 minutes, then continue to cool either at room temperature or in the refrigerator. 

Vanilla Frosting

1. Once the cake is cooled, make the frosting. In a large bowl using a hand or stand mixer, mix the shortening and butter until smooth (although it’s ok if it looks a little lumpy).
2. Mix in half of the powdered sugar, then the vanilla, then the remaining sugar. The frosting should be very thick at this point. Scrape down the bowl and mix in the water starting with 3 tablespoons. Once smooth, assess to see if the remaining tablespoon of water is needed.
3. Spread the frosting on the cooled cake and top with more sprinkles. Slice into 12 pieces and enjoy!