Toast the almonds in a non-stick frying pan.
Cut the chocolate into small cubes.
Blitz the almonds and pistachios in a food processor and mix with the chocolate.
Beat the egg whites with the salt until stiff, then add the sugar little by little, continuing to beat until the egg whites are glossy. Carefully stir in the bitter almond flavouring.
Fold the egg whites carefully into the almond, pistachio and chocolate mixture.
Using two teaspoons, form nuggets of dough approx. 3 cm in diameter and place them, spaced well apart, on two oven trays lined with baking paper. Dry at room temperature for approx. 3 hrs.
Dust the Amaretti with icing sugar and press each nugget lightly with 4 fingers to create the typical Amaretti shape.
for approx. 15 mins. in an oven preheated to 160 °C (convection). Remove from the oven, allow the Amaretti to cool on a rack.