I preheat the oven to 350°F (175°C) and grease a 9x13-inch baking dish, lightly dusting with flour. In a bowl, I sift 1 cup flour, 1 tsp baking powder, and ¼ cup cocoa powder. In a large bowl, I beat 5 eggs and 1 cup sugar with a mixer until thick and pale, about 7 minutes. I gently fold in the dry ingredients, then add ⅓ cup milk, stirring until just combined. I pour the batter into the pan, smooth the top, and bake for 22–25 minutes, until a toothpick comes out clean. I let the cake cool completely in the pan.

In a large measuring cup, I whisk together 1 can sweetened condensed milk, 1 can evaporated milk, ½ cup heavy cream, ⅓ cup strong coffee, and 2 tbsp cocoa powder until smooth and fully dissolved.

Using a fork, I poke holes all over the cooled cake. I slowly pour the mocha milk mixture evenly over the cake, letting it absorb gradually. I cover and refrigerate for at least 4 hours, preferably overnight, for maximum flavor.

Before serving, I beat 1½ cups heavy cream, ¼ cup powdered sugar, 1 tsp vanilla, and optional 1 tsp instant coffee until stiff peaks form. I spread the whipped cream evenly over the chilled cake.

I dust the top with cocoa powder or sprinkle with chocolate curls for a elegant touch, then slice and serve chilled.