In British English, beanfeast can refer to an annual dinner given to employees by their bosses or to any festive occasion or dinner.
In the afternoon [The Boys Brigade] were once again free to visit Blackpool arriving back at camp at 7:30 in time for the annual beanfeast. The beanfeast is an opportunity for the Boys to entertain their friends, both old and new. The highlights were Bugle playing, quiz, various challenges, songs, jokes and magic shows.
— David Knox, The Border Telegraph, 27 Aug. 2017
If you have seen the 1971 film Willy Wonka & the Chocolate Factory, you might recall that the spoiled-rotten character Veruca Salt wanted one. In the film, she sings "I want a feast, I want a beanfeast. Cream buns and doughnuts and fruitcake with no nuts, so good you could go nuts."
In the past, a beanfeast was a festival observed in parts of Europe on the evening before Twelfth Night. According to religious doctrine, Christmas festivities last until the twelfth day after Christmas—that is, until the Epiphany—the day commemorating the coming of the three kings to the infant Jesus Christ and during which people gave themselves over to feasting and merrymaking. One of the customs of Twelfth Night—the evening of Epiphany—was to make a special cake in which a bean was placed. The cake was then distributed and the man having the piece with the bean was crowned “king" for the night. Sometimes a pea was placed in the cake and the woman finding the pea in her piece was coronated "queen."
The chaplain of a ship of war left an enlightening record of such a Twelfth Night celebration in a January 6, 1676 entry of his journal:
For this day being 12 Day ... wee had much myrth on board, for wee had a great kake made, in which was put a beane for the king, a pease for the queen, a cloave for the knave.… The kake was cutt into severall pieces in the great cabin, and all putt into a napkin, out of which one took his piece, as out of a lottery, then each piece is broken to see what was in it….
— From The London Literary Gazette, 12 Mar. 1825