Trilece

Preheat the oven to 175°C (350°F) and grease a 9x13 inch baking pan. Beat the egg whites with an electric mixer on high speed until stiff peaks form, about 5 minutes. The peaks should stand straight up when the beater is lifted.

In a separate bowl, beat the egg yolks with 1 cup of sugar until pale, thick, and ribbon-like, about 4 minutes. Add the vanilla extract and mix briefly to incorporate.

Gently fold the sifted flour into the yolk mixture in three additions, using a spatula and turning the bowl as you fold. Then fold in the beaten egg whites in three additions, being extremely careful not to deflate the batter. The folding motion should be slow and deliberate.

Pour the batter into the prepared pan, spreading it evenly with the spatula. Bake for 25-30 minutes until the top is golden and a toothpick inserted in the center comes out clean. The cake should spring back when lightly pressed.

While the cake bakes, whisk together the whole milk, sweetened condensed milk, and heavy cream in a large bowl until fully combined. This three-milk mixture is the heart of the dessert and should be smooth and uniform.

Remove the cake from the oven and immediately poke holes all over the surface using a fork or skewer, spacing them about 2cm apart. Slowly pour the three-milk mixture over the hot cake, allowing it to absorb gradually. Refrigerate for at least 4 hours, or preferably overnight.

Make the caramel topping: combine 1 cup sugar and 3 tablespoons water in a clean saucepan over medium-high heat. Do not stir, but swirl the pan occasionally. Cook for 8-10 minutes until the sugar turns a deep amber color. Immediately pour the hot caramel over the chilled cake in a thin, even layer.

Let the caramel set for 10 minutes at room temperature, then return to the refrigerator until ready to serve. Cut into squares and serve cold, ensuring each piece has a generous layer of the crackling caramel on top.