Divide the 5 eggs between a yolk bowl and a mixer bowl for the whites. Keep the whites free of yolk so they can whip properly.

Warm the cream cheese, butter, and the batter's 1/4 cup sugar together in a pot over low heat, stirring gently. Continue until the mixture has an even consistency without visible cream cheese lumps.

Take the pot off the heat and gently work in the yolks. The mixture should look uniform, with no separate streaks of yolk.

Stir the cornstarch and flour into the yolk mixture until incorporated. Break up any pockets of dry flour before proceeding.

Blend in the milk and any optional flavoring you choose to use. The finished yolk batter should flow easily and look smooth, without needing a straining step.

Set the yolk batter aside and beat the egg white meringue ingredients to stiff peaks. Look for glossy foam whose peaks stand upright when you lift the beater.

Heat the oven to 330°F and place a deep rectangular baking dish containing water inside it. This dish will hold the cake pan or pans for the bain-marie bake.

Fit parchment circles into the bottoms of one 8-inch pan or two 6-inch pans, then line the inner walls with parchment strips. Use parchment paper, not wax paper, for the bottom liners and side collars.

Mix a portion of meringue into the yolk batter, then repeat with two more portions. These three additions lighten the batter before the final folding stage.

Transfer the lightened batter into the remaining meringue and fold gently until evenly combined. The mixture should resemble a thick milkshake with no white streaks, rather than separate foam and liquid layers.

Pour the folded mixture into the prepared pan or pans. It should remain airy and evenly blended as it settles.

Place the cake pans in the water bath and bake at 330°F for 25 minutes. If the cake isn't rising because the oven runs cool, a 10°F increase may be needed.

Check for a clear rise before changing the heat, allowing more time at the first temperature if necessary. The cake should have lifted noticeably before the second baking stage begins.

Open the oven door slightly for approximately 10 seconds, keeping your face clear of escaping steam, then lower the setting to 245–265°F and bake for another 45 minutes. Choose within that range to suit your oven, since excessive second-stage heat can split the surface.

Leave the cake in the oven for about 10 minutes after baking, then remove it carefully with oven mitts. The delicate cake benefits from this rest before handling.

Cover the cake with parchment and a plate, invert the assembly, and ease the pan away by sliding or gently shaking it loose. The cake's top should now rest against the parchment-covered plate.

Peel away the damp lining and replace the parchment on the exposed cake bottom. Remove the wet paper gently to avoid pulling away the tender crumb.

Position the serving plate against the cake bottom and carefully invert everything again. The cake should now sit upright, with its rounded top facing upward.

Serve the cake warm or refrigerate it for a chilled texture. Expect a bouncy warm crumb and a firmer, less jiggly chilled slice.