Use an edible marker to trace and cut parchment paper to fit your pan perfectly. We are using a 13" by 9" cookie sheet. Once the parchment paper is fit to the cookie sheet, trace the design that you want onto the prepared parchment paper using an edible marker.

Preheat the oven to 375 degrees Fahrenheit and grease a 13" by 9" cookie sheet with cooking spray and line with parchment paper. This makes three layers of sponge cake. You can also just use a standard-size cookie sheet, note that using a standard-size cookie sheet will only make two layers instead of three.

Separate the egg whites from the egg yolks. We are using every part of the egg in this recipe so hang onto both. Place the egg whites in a large bowl and the egg yolks into an even larger bowl. Set the egg whites aside, we will need them later.

Whisk together the egg yolks, sugar, vegetable oil, milk, and vanilla until smooth.

Sift the flour and cornstarch into the egg yolk mixture. Whisk until the batter is nice and smooth. The batter will be thick. Set aside.

In the bowl of a stand mixer fit with a whisk attachment, whisk the egg whites from earlier until frothy. Slowly add the sugar and vinegar to the egg whites.

Whisk the egg whites until stiff peaks form. This is very important. Stiff peaks should be able to stand up straight when the whisk is lifted.

Add the egg whites to the egg yolk mixture. Gently fold in the egg whites. Be careful not to over-mix the batter. Over mixing will deflate the egg whites and make the batter, thin and runny. Mix until the egg whites are evenly distributed and the batter has few streaks.

Use small bowls to dye each color that you will need to make your design. Scoop a bit of the batter at a time into these small bowls to make every color you need. Place each color into a piping bag.

Pipe the design with your desired colors. Do your best to trace the design that you created earlier with your piping bag.

Once you have the design finished, go ahead and freeze it for 5-8 minutes so it sets and is nice and firm.

Pipe the original, uncolored batter on top of the frozen design.

Bake for 8-9 minutes or until golden brown on the edges.

As soon as the cake comes out of the oven, flip the pan onto parchment paper. The design will be facing up. While the cake is still hot, peel off the parchment paper to reveal the beautiful design. Bake the remaining batter on the same-size cookie sheet. The other layers do not need designs since they will be hidden in the layers. They will bake the same way, on a greased cookie sheet for 8-9 minutes. Let the cakes cool completely before assembling.

To make the Whipped Cream, in the bowl of a stand mixer fit with the whisk attachment, whisk the cream, sugar, and vanilla until stiff peaks have formed and you have reached a whipped cream consistency. Fold in sprinkles, this is optional.

Once the cakes have cooled, layer the cakes with evenly spread whipped cream between each layer. Use the designed sheet cake as the top layer.

Feel free to trim the sides to clean it up a bit if you wish to give the cake a more complete look.