Beat the egg whites until stiff, allowing the sugar to trickle in. Keep beating until the mixture is very firm. Mix nuts and flour and fold in. Pour into a piping bag with a perforated spout.
Spray about 50 cookies onto a baking tray lined with baking paper. If necessary, press them flat. Bake in a preheated oven (electric: 150 °C/ gas: level 1) for 20-25 minutes. Dissolve the chocolate in a hot water bath and let it cool down a little.
Stir in amaretto, egg yolk, fat, icing sugar and almonds. Spread the filling over half of the biscuits and place the remaining biscuits on top, press lightly. Melt the chocolate coating in a hot water bath and decorate the cookies with it as you like.
Sprinkle immediately with the chopped pistachios. Results in about 25 pieces.