Oliver Cromwell banned Christmas pudding, mince pies and anything to do with gluttony. That law has never been rescinded so mince pies are illegal!

Christmas Puddings and Mince Pies were made to preserve meat using spices and fruits so they could be eaten during the lean months of winter.
You are correct in saying that It was banned but it was actually banned by the puritans in 1664 . Cromwell died in 1658 so it was nothing to do with him.
I think you owe Oliver an apology over that one.