PREP: Position a rack in the center of the oven and preheat the oven to 350ºF. Spray a 9x13 baking dish with cooking spray; set aside for now.
CAKE BATTER: In a small bowl, sift together the flour, cornstarch, baking powder, salt, and cinnamon. Then, repeat by sifting the mixture a second time; set it aside. In the bowl of a stand mixer, combine the eggs and granulated sugar. Using the whisk attachment, combine the ingredients on medium-high speed for 10-12 minutes or until pale yellow and fluffy. Then, stop the mixer check, and make sure the batter ribbons back slowly with a rubber spatula. Add the vanilla extract with the mixer running. Add ⅓ of the sifted flour mixture to the batter, and combine on the 'stir' setting. Repeat this step two more times until all the sifted flour mixture is added to the batter. Using a rubber spatula, scrape the bottom of the bowl to make sure there are no hidden flour pockets. Slowly stream in the oil with the mixer running. Pour the batter into the prepared baking dish, spread it out evenly. Bake for 25-28 minutes or until a toothpick inserted in the enter comes out clean. Remove the cake from the oven and let it to room temperature.
MILK: Prepare the milk mixture while the cake is cooling. In a large 4-cup measuring cup, whisk together the half and half, evaporated milk, and condensed milk until the condensed milk dissolves completely. When the cake has cooled, pierce the cake with a fork or a wooden skewer all over so that the milk mixture soaks up evenly. Slowly drizzle the prepared milk syrup evenly over the cake. Allow the cake to cool for several hours, covered in the refrigerator (at least 4 and ideally, overnight.)
WHIPPED CREAM: add heavy cream, granulated sugar, and vanilla to the bowl of a stand mixer, using the whisk attachment, whip on medium-high speed until soft peaks start to form; about 3-4 minutes. Allow mixer to keep mixing until the peaks are just slightly stiffer (about 15 seconds.) You can use a piping bag to pipe the whipped cream, or an offset/silicone spatula to spread on top. I like to use strawberries to decorate but pineapple, raspberries, or blueberries would all work well or you can serve on its own!