You can use a processor if you want to mix the ingredients but here are the instructions for making the dough by hand.
1. Sieve the flour into a large bowl and rub the butter into the flour until it resembles fine breadcrumbs.
2. Add the sugar, salt and ground almonds.
3. Add the 2 egg yolks and mix into the dough until it is smooth.
4. Place the dough in the refrigerator for about 1 hour to rest.
5. Roll out the dough on a lightly floured board until it is about 1/8 inch thick.
6. Use a small pastry cutter to cut out small round biscuits and place them on a lightly greased baking tray.
7. Brush lightly with egg.
8. Score the tops with a knife or a fork.
9. Sprinkle a little ground almonds in the centre and dust lightly with icing sugar.
10. Bake in a hot oven for about 8 minutes or when they are golden brown.
Cool on a wire tray and when cold keep in an air tight tin (if you can keep them - they won't last long!)