This is one of my favorite cakes- not just because it is dense and moist (from all 3 milks!) but because one 13x9 inch cake serves a lot of people. It can be made a day or two ahead and refrigerated. I usually spread it with plain whipped cream because it looks prettier that way and often add some strawberries. Everyone who tastes it wants the recipe and I always say "It's in Baking Basics and Beyond".
Here's The Recipe from Baking Basics and Beyond
Tres Leches Cake
This traditional Hispanic dessert is currently very popular in the United States. Tres Leches translates as “three milks,” and this cake is literally drenched in sweet milks—whipping cream, evaporated milk, and condensed milk. Whole milk is an extra!
MAKES 24 SERVINGS
2 cups all-purpose flour
2 teaspoons baking powder
1/4 teaspoon salt
3/4 cup butter, softened
1 1/2 cups sugar
4 eggs, separated
1 teaspoon vanilla
1 cup whole milk
1/2 teaspoon cream of tartar
3/4 cup whipping cream
1 (15-ounce) can sweetened condensed milk
1 (5-ounce) can evaporated milk
Heat oven to 350°F with rack in middle. Grease and flour a 13 x 9-inch baking pan.
Combine flour, baking powder, and salt in medium bowl.
Beat butter until creamy in bowl of a heavy-duty mixer on Medium speed. Gradually add sugar, scraping down sides of bowl occasionally, and beat 2 minutes. Beat in egg yolks, scrape down sides of bowl, and add vanilla. Beat 2 minutes more until mixture is very light and creamy.
Reduce mixer speed to Low. Add flour mixture in 3 additions, alternating with the whole milk in 2 additions. Scrape down sides of bowl after each addition. Beat until smooth, but no longer than 15 seconds.
Place egg whites and cream of tartar in bowl of a heavy-duty mixer fitted with the whisk. Beat on High speed until whites form soft peaks. (When you lift beaters, whites should form peaks that fall softly down.)
Add whites to batter with a folding motion. Bring a rubber spatula across the beaten whites in a motion parallel to the counter, slide the spatula down the back of the bowl, and pull it back in the other direction, lifting at the end. Rotate bowl as you fold. Pour batter into prepared pan.
Bake 30 to 35 minutes or until a toothpick inserted in center comes out clean. The cake may not be browned. Place cake pan on wire cooling rack and pierce cake generously with a fork or skewer.
Combine whipping cream, condensed milk, and evaporated milk in medium bowl and mix well. Spoon generously over the cake. Continue to add more liquid as topping is absorbed. You may not use it all. This cake must be stored in the refrigerator.
BAKER’S NOTES: It is easier to separate the egg yolks from the whites when the eggs are chilled. Do this about 1/2 hour before starting the cake.
Condensed milk has lots of sugar added, and evaporated milk does not—read the labels carefully.
SECRETS TO SUCCESS: Be sure bowl for beating egg whites is free from fat so that the whites will whip well.