Cut the butter into pieces. Put flour, salt and icing sugar in a bowl. Add butter and egg and knead first with the dough hooks of the hand mixer, then with your hands quickly to a smooth dough.
Wrap dough in foil and chill for about 30 minutes.
Bring jam to the boil in a small pot, then let it cool down. Roll out the short pastry on a floured work surface. Cut out small circles (approx. 6 cm Ø) with a cookie cutter. Cut a small circle (approx. 3 cm Ø) from half of the circles in the middle.
Knead remainders and process in the same way.
Spread circles and rings on 2-3 baking trays lined with baking paper and bake one after the other in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for 8-10 minutes. Take out and let cool down.
Spread circles with jam, leaving 2-3 mm of edge free. Dust the rings with icing sugar and place them on the jam.