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"Mrs. Weasley had sent Harry a scarlet jumper with the Gryffindor lion knitted on the front, also a dozen home-baked mince pies, some Christmas cake, and a box of nut brittle."
Mince pies are so called because they are filled with a spiced fruit mixture called "mincemeat", the latter itself being so-called because it traditionally included minced or shredded meat as well as the fruit. The mix nowadays consists of raisins/sultanas and similar spices to those used in Christmas puddings or cakes, often with candied orange peel as well, and in the case of luxury versions sometimes nuts or brandy.