The Polish doughnut traditionally filled with rose jam is called a pączek, or pączki in the plural.
Pączki are rich, filled doughnuts from Polish cuisine, usually made from yeast-raised dough and fried until golden. Wild rose petal jam is one of the classic fillings, along with powidła, a thick stewed plum preserve. Modern bakeries also use raspberry, strawberry, custard, cream, blueberry, apple, and other fillings.
These doughnuts are strongly associated with Tłusty Czwartek, or Fat Thursday, the Thursday before Ash Wednesday. The tradition reflects the custom of using up rich ingredients such as lard, sugar, eggs, and butter before the Lenten fast. Polish-American communities often celebrate a similar custom on Fat Tuesday, sometimes calling it “Paczki Day.”
The singular and plural can cause confusion: one pastry is a pączek, while several are pączki. The word is also commonly written without Polish diacritics as “paczek” or “paczki,” but those spellings refer to the same pastry. Unlike a ring doughnut, a pączek is normally closed and filled.