Certainly the most purists will find differences between biscotes, biscottis, carquinyolis or rosegones as they are called in Valencia but for me they are all delicious dry cookies with a nutty flavor.
Their main characteristic is that they are cooked twice, hence the biscottis thing. The whole roll is first cooked and then cut into slices that are returned to the oven for second cooking or roasting.
The normal ones is to make them with almonds but I am hooked on these of hazelnut. I love accompanying them with a Pedro Ximénez although they also serve to accompany a coffee or a hot chocolate.
They are perfectly preserved in a airtight jar or box and they say they can last up to 2 weeks or more. Personally, I have never had to wait that long because in a couple of days the boat is already empty.
Hazelnut Biscottis
The traditional biscuits, carquinyolis, rosegones or hazelnut biscottis are baked twice, which gives them a crunchy texture.
Equivalences with TM21
More information - Hot chocolate