"Tres leches" is Spanish for "three milks", and tres leches cake is a Mexican cake that is soaked in three kinds of milk/cream: evaporated milk, sweetened condensed milk, and heavy cream (although some recipes replace the heavy cream with whole milk). If the idea of a slightly soggy cake sounds disgusting to you, just think about the times you've had cake and ice cream together, and how good the cake is when the ice cream melts into it. Tres leches cake is quite similar, except that it's even more moist.
It was very difficult for me to find a recipe for this. I own dozens of cookbooks, but most of them don't have very many Mexican recipes in them. I have one cookbook that is entirely Mexican recipes, but tres leches cake was not included. So I had to search through cookbooks at libraries to find the perfect recipe. I finally found what I was looking for in Fresh Mexico by Marcela Valladolid.
This recipe says to use a 10-inch cake pan with 2-inch sides, and I only have 9-inch cake pans with 1.5-inch sides, so I had some batter left over. Even with leaving out a lot of the batter, the cake expanded more than I thought it would and spilled over a little bit, so I would suggest placing the cake pan on a baking sheet. I would do this even if I had the correct size pan just to be on the safe side.
I also didn't own any platters that had 1-inch high sides, so I just squeezed the cake into a 9x13 baking dish, which worked wonderfully.
Unsalted butter, for the pan
1 1/2 cups all-purpose flour, plus more for the pan
1 tbsp baking powder
1 tsp ground cinnamon
4 large eggs, separated
1 1/2 cups sugar
1/2 cup milk
One 14-oz. can sweetened condensed milk
One 12-oz. can evaporated milk
1 cup heavy cream
1 tbsp orange liqueur, such as Grand Marnier (I replaced this with about 1/2 tsp orange extract)
Preheat the oven to 350F. Butter and flour a 10-inch cake pan with 2-inch-high sides, and then line the bottom with parchment paper. Butter the paper.
Mix the flour, baking powder, and cinnamon in a medium bowl.
Using an electric mixer, whip the egg whites until frothy. With the mixer running, gradually add the sugar and beat until stiff peaks form. (I could NOT get this to stiffen, even after completely starting over, probably due to so much sugar being added. I decided to not worry about it, especially since it would collapse anyway after adding the other ingredients.)
Beat in the egg yolks, one at a time, blending well after each addition. Add the flour mixture in three additions, alternating with the whole milk in two additions.
Pour the batter into the prepared pan and bake for 30 minutes, or until a tester inserted into the center comes out clean. Let the cake cool slightly in the pan; then invert it onto a platter with 1-inch-high sides.
Pierce the top of the warm cake all over with a thick skewer.
Mix the sweetened condensed milk, evaporated milk, heavy cream, and orange liqueur (or orange extract), and pour over the cake.
Cover and refrigerate until cold, about 3 hours, or overnight.
Serve as is or top with whipped cream and/or fruit, if desired.
If you have never tried tres leches cake before, prepare to fall in love.