Set up a water bath without letting the water boil. Place a bowl with the egg whites and sugar on top.

Stirring constantly, dissolve the sugar in the whites. The mixture will reach about 60°C (140°F), but you can skip the thermometer: rub a drop between your fingers - you shouldn't feel any sugar grains.

As soon as the sugar has dissolved, take the bowl off the bath and start whipping. For icing, whip briefly - until smooth, with slow, stretchy ribbons falling from the whisk.

Add a pinch of citric acid and mix it in - that's it, the icing is ready! Glaze your kulich and pastries.