Sponge Loaf Cake

This classic sponge cake relies on vigorous egg beating to incorporate air, which expands during baking to create lift without chemical leaveners. Beating yolks and whites separately maximizes volume—yolks emulsify with sugar while whites whip to stiff peaks, trapping air bubbles. The potato flour (potato starch) contains no gluten, which keeps the crumb exceptionally tender by diluting the wheat flour's protein content and preventing toughness.