How to Make an Authentic Philadelphia Fluff Cake

Preheat your oven to 325°F (163°C). Prepare an 8-inch round cake pan by greasing it, lining the bottom with a parchment paper circle, and then greasing the parchment. Wrap the outside of the pan securely with a large, single piece of heavy-duty aluminum foil to create a waterproof seal.

In a medium, heatproof bowl set over a saucepan of simmering water (a double boiler), combine the cream cheese, milk, and butter. Whisk gently and consistently until the mixture is completely smooth and melted. Remove from heat and let it cool slightly for 5 minutes.

In a separate large bowl, whisk the egg yolks with 1/4 cup (50g) of the sugar until pale and creamy. Slowly stream the warm cream cheese mixture into the egg yolks while whisking constantly to temper the eggs. Whisk in the vanilla extract and lemon juice.

Sift the all-purpose flour, cornstarch, and salt directly into the cream cheese mixture. Whisk until just combined and no dry streaks remain. Do not overmix. Set this batter aside.

In the clean bowl of a stand mixer fitted with the whisk attachment (or using a hand mixer), beat the 6 egg whites and cream of tartar on medium speed until foamy. Gradually add the remaining 1/2 cup (100g) of sugar, one tablespoon at a time, while increasing the speed to medium-high.

Continue to beat the egg whites until they form soft, glossy peaks. When you lift the whisk, the peak should hold its shape but the tip should gently curl over. This is crucial; stiff peaks will make the batter difficult to fold and can result in a tougher cake.

Take about one-third of the whipped egg whites and gently fold them into the cream cheese batter to lighten it. Then, add the remaining egg whites and carefully fold until just combined. Work gently to avoid deflating the air you worked so hard to create.

Pour the final batter into your prepared cake pan. Place this pan inside a larger roasting pan. Carefully pour boiling water into the larger pan until it comes halfway up the sides of the cake pan, creating a water bath (bain-marie).

Bake for 60-70 minutes. The cake is done when the top is golden brown and the center has a slight jiggle to it (like set Jell-O). It will not be firm like a regular cake.

Turn off the oven, crack the oven door open slightly, and let the cake cool slowly inside the oven for 1 hour. This gradual cooling process is the ultimate secret to preventing cracks.

Remove the cake from the oven and the water bath. Let it cool completely on a wire rack at room temperature before running a thin knife around the edge and inverting it. Peel off the parchment paper, then re-invert it onto a serving plate. Chill for at least 4 hours before serving for the best flavor and texture.