01 - Preheat oven to 350°F. Grease and flour a 9x13-inch baking dish.
02 - In a bowl, whisk together flour, baking powder, and salt. Set aside.
03 - In a large bowl, beat egg yolks with 3/4 cup sugar until pale and thick. Stir in milk and vanilla extract.
04 - Gently fold the flour mixture into the yolk mixture until just combined.
05 - In a clean bowl, beat egg whites to soft peaks. Gradually add remaining 1/4 cup sugar and continue beating until stiff peaks form.
06 - Gently fold the egg whites into the batter in three additions, maintaining as much volume as possible.
07 - Pour batter into prepared pan and spread evenly. Bake for 30 to 35 minutes, or until a toothpick inserted in the center comes out clean.
08 - Let cake cool in the pan for 10 minutes. Pierce all over with a skewer or fork.
09 - In a large measuring cup, whisk together coconut milk, eggnog, and sweetened condensed milk.
10 - Slowly pour the milk mixture evenly over the cake. Allow to cool to room temperature, then refrigerate for at least 2 hours.
11 - Beat heavy cream with powdered sugar and vanilla using an electric mixer until soft peaks form.
12 - Spread whipped cream across the chilled cake, then sprinkle with toasted coconut.
13 - Slice and serve cold for optimal texture and flavor.