Time to get it straight once and for all. When do you / do you not make a Brocho on dessert in a meal (where you washed)?
There are a lot of different practices (and I believe a stira in the Mishna Brurah), and it may depend on your practice.
Here's what I was told in yeshiva:
Fresh fruit (including "ha'adama fruit" like watermelon and bananas), candy, ice cream -- all get a bracha.
Anything mezonos, anything liquid, cooked fruit -- included with the meal.
According to Sephardi poskim all deserts require their own blessing. In most sephardi homes on shabat they typically strive to bring out something for each of the berakhot(mezunot, eitz, adamah, hakol).
Regarding mezonos (mentioned quickly in a comment on a different answer):
Bread is Hamotzi, and therefore one doesn't make a beracha on it since it is included in the Hamotzi at the beginning of the meal. Cake is Mezonos and one would make a beracha on it when it is eaten as dessert.
The question of making a beracha on a mezonos dessert depends on what is considered "Pas/Bread" vs. "Pas Haba BeKisnin/Cake". There are 3 possibilities cited in SH"A (really simplifying here):
- Sweetened dough
- Filled dough
- Hard dough
If the desert you're eating satisfies all three, it is definitely a Mezonos (and not a Hamotzi) and therefore one makes a Mezonos when eaten as dessert. A good example are hamentaschen.
However, if it satisfies only one (possibly even two) of the conditions, no beracha.
According to the Sephardim, one is Lechtechila not allowed toto eat cakes or cookies during a meal of bread (Yalkut Yosef, Heleq 3, page 187). He says you must wait until after you finish Birkat HaMazon. EDIT: Because some cakes are Hamotzi and some are Mezonot. This Halacha has a lot of cirumstances. http://www.dailyhalacha.com/displayRead.asp?readID=1571&txtSearch=eating%20cake%20meal See this for more details.