Preheat oven to 350°F and generously butter a 9×13-inch casserole dish. Arrange three separate mixing bowls. In one bowl, sift together the flour, baking powder, and salt. In the other bowls, separate the egg whites from the yolks. Using an electric mixer, beat the egg yolks with 3/4 cup sugar on high speed until pale and thick, about 2 minutes, then blend in the whole milk and vanilla extract. Whip the egg whites on high until soft peaks form, then gradually add the remaining 1/4 cup sugar while mixing until stiff but not dry. Pour the yolk mixture into the dry ingredients, folding gently to combine. Carefully incorporate the beaten egg whites using a spatula until fully integrated. Transfer the batter to the prepared pan, smoothing the surface evenly. Bake for 30–35 minutes or until a toothpick inserted in the center emerges clean.

For the soaking syrup, whisk together the evaporated milk, condensed milk, and heavy whipping cream in a large measuring cup or jug. Once the cake has cooled slightly, pierce the surface thoroughly with a fork. Gradually pour the milk mixture over the cake, ensuring it absorbs fully. Allow the cake to rest for at least 30 minutes, or cover and refrigerate overnight for deeper flavor.

For the frosting, combine cold heavy whipping cream and granulated sugar in a chilled mixing bowl. Beat on high speed for about 1½–2 minutes until the cream is thick and spreadable. Evenly frost the cake with the whipped cream, smoothing it out with a spatula. Garnish with fresh berries if desired.