Step 1: Preheat your oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan. In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
Step 2: In a large bowl, using an electric mixer, beat the egg yolks with 1 cup of the granulated sugar until light and fluffy, about 3-4 minutes. Stir in the 1/2 cup whole milk and 1 teaspoon vanilla extract until well combined.
Step 3: In a separate, clean large bowl, beat the egg whites with the remaining 1/2 cup granulated sugar until stiff peaks form, about 4-5 minutes. Gently fold the egg white mixture into the egg yolk mixture in three additions, being careful not to deflate the whites. This creates the airy base for your tres leches cake recipe.
Step 4: Gradually fold the dry ingredients into the egg mixture until just combined. Pour the batter into the prepared baking pan and spread evenly. Bake for 30-35 minutes, or until a wooden skewer inserted into the center comes out clean. Let the cake cool completely in the pan on a wire rack. Once cooled, poke holes all over the cake using a fork or a wooden skewer.
Step 5: While the cake cools, prepare the three milk mixture. In a medium bowl, whisk together the evaporated milk, sweetened condensed milk, and 1 cup of heavy cream, along with 1 teaspoon of vanilla extract. Make sure it's thoroughly combined.
Step 6: Slowly pour the milk mixture evenly over the cooled, poked cake. Allow the cake to soak up all the liquid, which may take 15-20 minutes. For best results, cover the pan with plastic wrap and refrigerate for at least 4 hours, or preferably overnight, to allow the cake to fully absorb the milks and develop its rich flavor. This is key for a perfect tres leches cake recipe.
Step 7: Just before serving, prepare the whipped cream topping. In a large, chilled bowl, beat the remaining 1 cup of heavy cream with 1/4 cup granulated sugar and 1 teaspoon vanilla extract until stiff peaks form. Spread the whipped cream over the top of the chilled tres leches cake recipe.
Step 8: Garnish with a sprinkle of ground cinnamon or fresh berries, if desired. Cut into squares and serve immediately. Enjoy your homemade tres leches cake recipe!