How to fold whipped egg whites into cake batter
Lighten a dense base first so the remaining foam can be folded through with less effort.
Choose a broad spatula that can reach the bottom of the bowl. Take a small portion of the whipped whites and stir it into the heavier base. This first portion loosens the mixture. It is easier to fold the rest of the whites into a base that already flows a little.
Add part of the remaining whites. Cut the spatula down through the center, sweep along the bottom and turn a ribbon of the heavier batter over the foam. Give the bowl a small turn after each stroke. Watch the base of the bowl, where a thick patch of batter can hide below a pale, apparently mixed surface.
Fold in the final portion and stop when you no longer see large white streaks or heavy unmixed pockets. Transfer the batter to the prepared pan promptly, scraping it in a few broad motions to preserve the air you worked into it.
