To eat tiramisu is like eating tenderness itself, slightly tampered with bitter cocoa. To make it exactly like this, use a special technique of mixing whites into the dough - "folding". This technique is essential for airy desserts such as tiramisu, mousses, soufflés, and biscuits. It allows you to keep as much air from the egg whites as possible: you need to put a lighter mass into a heavier one, folding it in a certain way. To do this, take a large, wide bowl, transfer a heavy mass into it, put ¼ whites on top and stir intensively but gently with a silicone spatula. Some of the air will "escape", but the mass will become thinner and lighter, which will help you mix in the remaining whites. Then lay out the remaining whites, use a spatula to "cut" the mass vertically in half and fold the left half of the mass from the bottom up to the centre of the bowl. At the same moment, rotate the bowl counter clockwise with your other hand if you are right-handed. Again "cut" the dough in half and repeat the movement, carefully folding the next portion of the mass. Repeat until the mixture is smooth. Be careful and take your time trying to preserve as much as possible the amount of whipped air.