Step 1: The Cake Pan Prep

Preheat your oven to 350°F. Grease your 9×13 pan generously with butter or cooking spray, then dust it lightly with flour. Tap out the excess. This cake is delicate—you don’t want it sticking. Some people line the bottom with parchment paper for extra insurance. Do what makes you feel safe.

Step 2: The Dry Ingredients

In a medium bowl, whisk together the flour, baking powder, and salt. Set aside. This is the easy part. Don’t skip sifting or at least whisking—lumps in sponge cake are sad.

Step 3: The Egg Yolk Situation

Separate your eggs carefully—no yolk in the whites or they won’t whip properly. In a large bowl, beat the egg yolks with 3/4 cup of the sugar using an electric mixer on high speed for about 3-5 minutes until thick, pale yellow, and fluffy. It should form ribbons when you lift the beaters. Add the milk and vanilla, beating until combined.

Step 4: The Dry Meets Wet

With the mixer on low speed, gradually add the flour mixture to the egg yolk mixture, beating just until combined. Don’t overmix—overmixing makes tough cake and sponge cake should be tender. The batter will be thick. This is correct.

Step 5: The Egg White Magic (Most Important Step)

In a completely clean, dry bowl (any grease or water will ruin this), beat the egg whites with an electric mixer on medium speed until soft peaks form. Gradually add the remaining 1/4 cup sugar while beating, then increase speed to high and beat until stiff, glossy peaks form. This takes about 3-5 minutes. Don’t underbeat—you need stiff peaks for the cake to rise properly.

Step 6: The Folding Process (Be Gentle)

Add about 1/3 of the beaten egg whites to the batter and fold gently with a spatula to lighten it. Then add the remaining egg whites and fold gently until just combined. The key word is GENTLE—you’re trying to keep all that air you just beat into the whites. Use a folding motion, not stirring. Some white streaks are fine. Fold in the crushed Oreos at the very end.

Step 7: The Baking

Pour the batter into the prepared pan and spread it evenly. Bake for 25-30 minutes until the top is golden and springs back when lightly touched, and a toothpick inserted in the center comes out clean. Don’t overbake—sponge cake dries out easily.

Step 8: The Cooling (Patience Required)

Let the cake cool in the pan for about 10 minutes. It’ll deflate slightly—this is normal for sponge cake. Don’t panic. Once it’s cooled slightly, use a fork or wooden skewer to poke holes all over the cake—like, EVERYWHERE. Every inch should have multiple holes. These holes are how the tres leches mixture gets into the cake. Don’t be shy.

Step 9: The Tres Leches Mixture

While the cake cools, whisk together the sweetened condensed milk, evaporated milk, heavy cream, vanilla, and the finely crushed Oreos in a large measuring cup or bowl. Mix until the Oreo crumbs are suspended in the liquid. If you’re adding espresso powder, add it now.

Step 10: The Soaking Process (The Magic Happens)

Slowly pour the tres leches mixture evenly over the entire cake, making sure to get the edges and corners. It will look like way too much liquid. That’s the point. The cake will absorb it. Pour slowly, pausing between pours to let the cake absorb. Use all of the mixture—don’t hold back. The cake should look like it’s sitting in a puddle. This is correct.

Step 11: The Overnight Situation

Cover the pan tightly with plastic wrap and refrigerate for at least 4 hours, but preferably overnight. This is NOT optional. The cake needs time to absorb all that liquid and for the flavors to meld. Overnight is better than 4 hours. Two nights is even better if you have the patience.

Step 12: The Whipped Cream Topping

When you’re ready to serve (not before—whipped cream deflates over time), make the topping. In a cold bowl with cold beaters, whip the heavy cream on medium speed until it starts to thicken. Add the powdered sugar and vanilla (and pudding mix if using for stability). Increase speed to high and beat until stiff peaks form. Don’t overbeat or you’ll have butter.

Step 13: The Final Assembly

Spread the whipped cream evenly over the entire cake using an offset spatula or the back of a spoon. Cover every bit of cake—this is your canvas. Sprinkle the crushed Oreos generously over the whipped cream. Like, really generously. This is cookies and cream tres leches—the Oreos should be visible from space. Arrange whole Oreos decoratively on top. Drizzle with chocolate syrup if you’re feeling fancy.

Step 14: The Serving

Cut into squares and use a spatula to lift them out. The cake will be very moist—almost pudding-like at the bottom, more cake-like at the top. This is intentional. Serve on plates with a spoon because there will be extra milk at the bottom and you’ll want to eat every drop.

Step 15: The Eating

Take a bite and experience the impossibly moist, milk-soaked cake. Notice how it’s not soggy or gross, just incredibly tender and creamy. Taste the Oreos throughout—in the cake, in the tres leches, on top. Feel the cool whipped cream. Taste the sweetness from three kinds of milk. Immediately want another piece but remember you’re in public and should show restraint.