There is a widespread custom to eat "Sufganiyot," or fried jelly donuts, on Hanukah. Since the Hanukah miracle involved a jug of oil, Jews have traditionally included oily foods such as jelly donuts in their Hanukah celebration.
Before one eats a jelly donut he of course recites the Beracha of "Bore Mine Mezonot." If, however, one eats a jelly donut as part of a bread meal, the Beracha of "Ha'mosi" that he recited over the bread at the beginning of the meal covers the donut, and thus he does not recite a Beracha over the donut. Nevertheless, given the difference of opinion among the authorities on this issue, Hacham Ovadia Yosef (Hazon Ovadia Hanukah, p. 19) writes that one should preferably eat the donut after Birkat Ha'mazon. Waiting until after the recitation of Birkat Ha'mazon ensures that one will be required to recite the Beracha of "Mezonot" according to all opinions, which is preferable to putting oneself in a situation of Halachic uncertainty.
Generally speaking, a person who eats a very large amount of cake 8 oz. or more is considered to have eaten a meal and must therefore recite Birkat Ha'mazon. Even if he did not partake of any bread, he must recite Birkat Ha'mazon because the consumption of this quantity of cake constitutes "Kevia't Se'uda" establishing a formal meal, which requires Birkat Ha'mazon. Rabbi Efrayim Navon, author of the Halachic work "Perah Shushan," rules (on the basis of a ruling of Rabbenu Shimshon, cited by Tosefot in Masechet Berachot) that this Halacha does not apply to fried foods. According to this view, flour-based foods such as donuts which are fried, rather than baked, never require the recitation of Birkat Ha'mazon regardless of the quantity of which one partakes. Hence, Hacham Ovadia Yosef writes (Hazon Ovadia Laws of Berachot, p. 66; listen to audio for precise citation) that one does not recite Birkat Ha'mazon after eating jelly donuts, even he ate a quantity exceeding 8 oz. Even though jelly donuts are often very filling, and the consumption of 2-3 donuts generally leaves one fully satiated, he nevertheless recites "Al Ha'mihya" and not Birkat Ha'mazon. (This would apply to other fried pastries, as well, such as "Zalabiye.")
Is it permissible to place a jelly donut on an electric hot plate or "blech" (sheet of metal covering the stove) on Shabbat so that it could be eaten warm?
Generally speaking, Halacha permits reheating on Shabbat dry foods that have already been cooked, but not liquids. Seemingly, then, it should be forbidden to warm jelly donuts on Shabbat because the jelly inside is liquid, and, as mentioned, one may not reheat liquid foods on Shabbat. However, Rabbi Shlomo Zalman Auerbach (Jerusalem, 1910-1995), as cited by Hacham Ovadia Yosef (listen to audio for precise citation), ruled leniently in this regard. He maintained that the jelly is seen as subordinate to the dry donut and may thus be reheated together with the rest of the donut.
Summary: It is customary to eat jelly donuts during Hanukah. One who partakes of a jelly donut recites beforehand the Beracha of "Mezonot," unless it is eaten as part of a bread meal, in which case it is covered by the Beracha recited over the bread. Preferably, however, donuts should be eaten only after Birkat Ha'mazon with a Beracha. After eating jelly donuts one recites "Al Ha'mihya," even if he ate several donuts and feels fully satiated. It is permissible to warm jelly donuts on a hot plate or "blech" on Shabbat.
