Sablés de Bourg-Dun

Sift the flour on to a marble slab or board and make a large well in the centre. Put the egg yolks, salt, sugar and orange or lemon rind and juice in the well. Pound the butter to soften it slightly; then add it to the well and use the fingertips of one hand to work it quickly with the other ingredients until partly mixed. Gradually incorporate the flour, using the whole hand. Knead the dough w