Work plain flour, baking powder, sugar, butter, vanilla sugar, salt and eggs into a smooth dough. Wrap and chill for 2 hours.
Preheat oven to 200 C / Gas 6.
Roll dough out and cut out 5cm circles. Cut smaller circles out of the middle of half of the circles.
Place on a baking tray lined with baking parchment and bake for 10-12 minutes or until lightly golden.
Spread jam over the whole circles while they're still warm. You scan strain it through a sieve first, if you like. Dust the rings with icing sugar and place one on each whole circle covered with jam. Leave to cool completely.