Stir up Sunday is 23rd November... traditionally, the victorians would go to church and by an association of ideas would go home and 'stir up' the Christmas puddings and cakes.
The activity of stirring-up the ingredients symbolizes our hearts that must be stirred in preparation for Christ's birth.
The batter needs to be mixed up well, and everyone in the family and guests should give a good stir. Plum puddings are a classic Christmas dessert, as in Bob Cratchit's Christmas dinner in Charles Dickens'
A Christmas Carol.
Plum puddings are similar to fruitcake, except they are more like a rich, dense spice cake. The pudding contains many candied fruits, lemon and orange peels, raisins and currants. After stirring up the pudding, it is then steamed this day, but not consumed until Christmas. Waiting until Christmas day gives the "aging" so the full flavor will be experienced. Serve with the delicious plum pudding sauce over the top.
For fun, add tokens into the stirred batter before steaming. Each token has significance for the finder.
Insert items like a coin
(wealth in the new year), silver charms in shape of a button
(person will be bachelor for another year), a thimble
(spinsterhood for another year), a horseshoe
(good luck), a ring
(marriage in the upcoming year) and so on. These items can also be wrapped in aluminum foil so they will be easier to find when eating the pudding.
(Details collected from catholicculture.org)
The collect for the day from the Book of Common Prayer
Stir up, we beseech thee, O Lord, the wills of thy faithful people; that they, plenteously bringing forth the fruit of good works, may of thee be plenteously rewarded; through Jesus Christ our Lord. Amen.
The Feast of Christ the King
Dear Father, stir up our wills that we may get on with doing all the good works that you have planned for us to do.
Jesus is King, Lord of all! Amen! 
