Contributed by: Rabbi Alouf
When Pourim falls on Ereb Shabbat, there are two different methods to fulfill the missvah of Seoudat Pourim.
Recommended Method: Seoudat Pourim is a Seoudat Missvah, and therefore one may establish one's meal even after Hassot Hayom (midday: 1:03pm) on Ereb Shabbat [Rama Siman 249 in Orah Hayim]. However, if it is possible to start a half hour before midday (12:33pm) it preferable to do so, before the obligation to pray Minha even begins (according to all posqim).
One may enjoy the meal, leaving plenty of time until the onset of Shabbat, ensuring that one will have an adequate appetite for the Shabbat meal.
"Pores Mappah OuMeqadesh" Method: This method effectively combines Seoudat Pourim with Seoudat Shabbat into one extended meal. Pray Minha earlier in the day, anytime after midday, and begin the meal approximately 6:30pm. Make Nitilat Yadayim, blessing on bread, enjoy wine & meat for the missvah of Seoudat Pourim. Interrupt the meal for candle lighting at 6:50pm, cover the table and food with a tablecloth (or at least just cover the bread), and make Qiddoush without the blessing of Hagefen on the wine. Say Yom Hashishi followed by the blessing of Meqadesh HaShabbat only! The blessing on the wine is not repeated, because one already made the blessing on wine for Seoudat Pourim. Qabbalat Shabbat is not said at the table because Qiddoush serves as the Qabbalat Shabbat. Then remove the tablecloth, and complete the meal, with bread (at least kazayit). When making Birkat Hamazon be sure to recite Al HaNisim and Resseh VeHaHalissenou. Then one must pray Arbit.
The Mahariqash mentions both methods in Erech Lehem, as does Harav Hagaon Refael Aharon Ben Shimon in the Nehar Missrayim, a work describing our Egyptian customs. It seems that the second method of "Pores Mappah OuMeqadesh" was common among knowledgeable individuals, familiar with the intricate details and requirements of performing Seoudat Pourim in this manner.
If one wishes to perform "Pores Mappah OuMeqadesh", there are two important caveats one must be aware of:
1) One must not begin the meal too early, thereby making the Qiddoush for Shabbat after the meal is effectively over, because there are halachic ramifications not described in this article. One must eat after Qiddoush as well.
2) This method does not permit anyone to pray Arbit of Shabbat without a minyan.