The object of twice baked cookies is to dry them out completely to extend their shelf life.
Here we have zwieback, or Holland Rusk, which is slightly sweet spice bread that has been baked, sliced, and then dried out.
What we normally refer to as Italian biscotti is an elongated cookie that has been baked, cut, and then put back in the oven. Starbucks has them sitting out as an impulse item for us to buy and dunk in our coffee.
Biscotti di Prato, or cantucci which are made in a similar manner. These cookies, although you will find recipes made with butter, are traditionally made only with sugar, flour, and eggs with the addition of nuts and dried fruit. The dough can be hard to handle. It is necessary to knead it a bit. And, because the addition of nuts is not easy, a neat trick is to roll the dough out and then place the nuts onto it before kneading it some more.
The dough is then formed into cylinders and is ready for the first baking, before it is cut into slices and placed back in the oven.
Don’t give up on biscotti. They are a little difficult to manage, but because of its keeping power make great things to have on hand and to give as gift.