Prepare Italian meringue. In a bowl with a thick bottom, add sugar, citric acid and water. Put the syrup on the fire and bring to a boil, stirring. During boiling, all sugar crystals should dissolve.
When the syrup boils, reduce the heat and cook to 120 degrees (the dough will make a solid ball). Make sure that the syrup does not boil too much and does not begin to acquire a caramel color.
In parallel, whisk the whites into a strong foam and, continuing to whisk them, pour in a thin stream of sugar syrup, brewing the whites.
Proteins with the introduction of syrup will significantly increase in volume, meringue will become shiny, glossy. Beat the meringue until it cools down.Decorate the brownie blanks with meringue. It will already be quite elegant.