Whisking egg whites traps air in them, increasing their volume. The air in whisked egg whites helps cakes, soufflés and other dishes to rise.
-Set the electric whisk to a slow speed and whisk the egg whites until foamy.
-Increase the speed of the whisk, moving the beaters around the bowl as you whisk the egg whites.
-Continue to whisk until peaks form when the whisk is removed (these will be soft or stiff, depending on the recipe). If stiff peaks are required, the eggs should be so firm that they do not slip out of the bowl when you tilt it.
Source: https://www.bbc.co.uk
