The Minhag on Chanukah is to eat foods that were fried in oil. It seems that this is part of the remembrance of the miracle that took place with oil. There is also a custom to eat donuts, more specifically jelly donuts that are fried. So it is worthy to say one Halacha regarding the jelly donuts.
Is the Beracha of Mezonot required before eating jelly donuts if it is the dessert of a meal for which you washed and made HaMotzih?
We are familiar with the Halacha that says the HaMotzih covers most foods that are used for dessert. This includes normal Mezonot items like cakes and cookies. The HaMotzih covers these items because we are not sure if they are definitely considered "Pat Haba'a Be-Kisnin", which is when we say Mezonot. Now there is a debate as to what constitutes "Pat Haba'a Be-Kisnin." Some Rabbis say it is considered "Pat Haba'a Be-Kisnin" when it is kneaded with honey or sugar like a cookie. Others say it is when the food has the properties of a pocket type structure like a turnover. And yet others say it is when the food is crunchy like a pretzel. So since there is doubt as to which of these constitute a Mezonot, we therefore accept upon ourselves that the HaMotzih covers desserts such as cakes, cookies, turnovers, pretzels, etc. (For further understanding of this, please see the Daily Halacha entitled "When One Must Say Birkat Mezonot after saying Birkat HaMotzih.")
However, with regards to the fried jelly donut, there is no controversy among the Poskim. A jelly donut qualifies as a definite Mezonot. Firstly because it is fried and according to most Poskim, fried makes it a Mezonot. Furthermore it is sweet and the property of a pocket. Therefore it qualifies as a Mezonot even after one made HaMotzih in the seuda.
Halacha Lema'ase, according to the Birkat Hashem in Helek 3, Page 375 (written by Rabbi Moshe HaLevi), if one is eating a fried jelly donut as a dessert to a meal for which he washed and made HaMotzih, he nonetheless must make a Mezonot because the HaMotzih does not cover the jelly donut.