In a medium bowl, whip the eggs and sugar with an electric mixer at high speed. Mix for 6 to 10 minutes, until mixture is thick and pale. Combine the flour and baking powder together. Gradually add the flour to the egg mixture. If the dough is still sticky, you can add more flour.
On a lightly floured surface, roll the dough into long log shapes, about 4cm in diameter, and as long as your cookie tray. Cover with a clean towel, and let them sit out overnight.
Preheat oven to 190 degrees C (375 degrees F). Remove the rolls of dough from the cookie trays and place them on a lightly floured surface. Cut into 4cm long pieces. And return them to the baking trays.
Bake for 15 to 20 minutes in the preheated oven, until they are a light brown. Remove from baking trays to cool on wire racks. These cookies can be stored for a month in an airtight container.