Sieve the icing sugar into a mixing bowl. Add almonds, egg white and flavour. Stir with the whisks of the mixer for about 4 minutes.
Line two baking trays with baking paper. Preheat the oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Form approx. 48 walnut-sized balls from the dough with moistened hands and place them on the baking trays.
Lightly press the round surface of the balls with three fingertips. Let it rest overnight at room temperature.
Bake the Amarettini one after the other in a hot oven for about 20 minutes. Take them out of the oven and let them cool down on the baking trays. Dust with icing sugar. Individually wrapped in tissue paper, they last 3-4 weeks.