The Christmas celebration consists of many traditions. Milk used to be only a seasonal product, so many people put out porridge for Santa on Christmas Eve. Those who have a barn put out the porridge for the barn Santa. Barn Santa is more picky and can often be in a slightly worse mood than Forest Santa and Father Christmas. The Santa Claus can get grumpy if he doesn't get porridge on Christmas Eve, and then the Santa Clauses can make noise in the barn and mess it up. (source)