Preheat oven to 325F. Cream butter and icing sugar together. Add the vanilla. Slowly add in the flour. Form into a ball and cover with plastic wrap. Place in the refrigerator for 30 min. if too soft. Otherwise roll out on a lightly floured surface to ¼" thick and with a 1" round cookie cutter cut out circle.
Alternately roll into multiple 1" wide logs and slice into ¼" thick pieces.
Either way, immediately press gently into small round festive coloured sprinkles and then place on a cookie tray with a Silpat liner or parchment.
Bake for 15 min. or until lightly golden brown. Remove to cooling racks. When cool, remove to a sealed cookie container, layered with wax paper. Freezes well for up to 2 months.