Preheat your oven to 325 F / 170 C / Gas Mark 3. Sift the flour, salt and icing sugar into a large bowl. Add the butter and using your finger tips rub the butter into the flour until thoroughly incorporated and the mixture resembles sand or breadcrumbs.
Mix the egg yolks together and add into the flour and butter. Using a folk mix together to form a dough. Wrap the dough in cling film and chill in the fridge for at least an hour.
Place the pastry onto a lightly floured work surface. Using a lightly floured rolling pin carefully roll out so the pastry a half a centimetre thick. Cut into rounds with a four-centimetre cookie cutter.
When all of the pastry is cut, divide the sable biscuits in two. Using a small fluted cutter, make a hole in the middle of half of the sable biscuits. Place all the sables on a lined baking tray.
Bake the sables for ten minutes or just a little more, or until light golden-brown and crisp. Remove from the baking tray carefully place on a cooling rack.
Using a teaspoon, place a small dollop jam on a whole sable. Place a biscuit with a hole over the first biscuit and sandwich together. Repeat until all the biscuits are finished with your choice of jam. Dust with icing sugar and serve.