Melt butter in a pot. Add honey, remove from heat and let it cool down. Sieve the icing sugar into a bowl. Add flour, baking powder and ground almonds and mix. Stir in the egg white first, then the butter-honey mixture. Cover and put in the fridge for at least 6 hours
Chop the pistachios finely. Grease 6 box-shaped baking trays (each containing approx. 250 ml) of a baking tray and dust with flour. Spread the dough inside. Sprinkle the pistachios on top and bake in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for 20-30 minutes. Remove from the tins and let cool on a cake rack
waiting time approx. 6 hours