Mix the flour, sugar and salt in a bowl. Add the butter and rub together using your hands to form an even, crumbly mixture. Add the egg, mix quickly to create a soft dough – do not knead. Flatten the dough, cover and chill for approx. 30 mins.
To shape the cups
Roll out the dough to approx. 3 mm thick between two sheets of baking paper, cut into strips measuring approx. 6 x 15 cm. Line the sides of the rings with the dough strips, press gently. Combine the rest of the dough, roll out to approx. 3 mm thick. Place the metal rings on top and use to cut out the bases, transfer to a baking tray lined with baking paper, chill for approx. 30 mins. Prick the pastry bases firmly with a fork.
Approx. 15 mins. in the lower half of an oven preheated to 200°C. Remove from the oven, leave to cool on a rack, remove the cookie cups from the rings.
Place the couverture drops in a thin-sided bowl and suspend over the gently simmering bain-marie, ensuring the bowl does not touch the water. Melt the chocolate and stir until smooth. Coat the inside of the cups with chocolate. Gently dip the edges in the chocolate, decorate with chocolate sprinkles or nuts. Chill for approx. 30 mins.
Pour coffee or milk into the cookie cups. Drink the coffee and eat the cups.