Mix together vanilla seeds, butter, sugar, eggs yolks and salt. Work flour and hazelnuts into the mix and knead into a dough. Wrap and chill for 2 hours.
Preheat oven to 200 C / Gas 6. Grease or line a baking tray with baking parchment.
Shape the dough into a long roll and cut into even slices. Roll each slice into a ball and press a small dent into each ball using the end of a spoon. Transfer to the prepared baking tray and bake for 12-15 minutes on the middle shelf.
Let biscuits cool on the tray for a few minutes, before transferring them to a wire rack to cool fully.
Meanwhile, heat jelly in a pan over low heat. Stir until smooth. Dust cold biscuits with icing sugar and fill with warm jam.
Very easy, made them with a friend and her little brother(who is 6) and we had great fun. Watch them in the oven at all times because they can easily burn. Replace redcurrant jam with strawberry. We made ours into funky shapes, but its's best not to do that as they go wrong quite easily. - 08 Oct 2011