Cut and fold is the gentle mixing technique used to blend dry ingredients — or a light foam such as whipped egg whites — into a batter without knocking the air out. The cook cuts down through the centre of the mixture with a spatula or metal spoon, sweeps under it, and folds it back over the top, turning the bowl a quarter-turn between strokes. The motion distributes flour or foam evenly while keeping the bubbles that give sponges, soufflés, and mousses their lift. Stirring or beating would develop gluten in the flour and collapse the foam, producing a dense, rubbery crumb instead of a light one. The technique is a small skill with an outsized effect: whole classes of cakes and aerated desserts succeed or fail on whether the folding was done with a light, patient hand.