Melt butter at low heat. Stir with sugar, 1 pinch of salt and cinnamon until creamy. Stir in juice and rum. Fold in flour, oat flakes and almonds. Cover and chill for about 1 hour.
Place a teaspoonful of heaps with enough space between them (dough runs apart during baking!) on trays lined with baking paper. Bake in the preheated oven (electric cooker: 175 °C/circulating air: 150 °C/gas: level 2) for approx. 12 minutes. Let them cool down
Chop the chocolate coating and melt in a hot water bath. Dip cookies into it and let them dry on a cake rack