Christmas Pudding Puzzle

Father Christmas spends 364 days of the year as a taster of Christmas puddings (which is why he is so round and jolly). Recently he came across a Magic Pudding.

If you eat some of this pudding, the next thing you say comes out in a magic code.

Father Christmas tried it, liked it, and said:

"IP! IP! IP! XIBU B MPWFMZ QVEEJOH! NFSSZ DISJTUNBT BOE B IBQQZ OFX ZFBS UP ZPV BMM!"

What did he say?