Cream butter, add sugar gradually, beat until light & fluffy. Add well beaten egg, vanilla & milk. Add sifted SR flour, mix well. Gradually mix in sifted plain flour until dough is firm enough to handle. Refrigerate at least 1 hour. Roll out to 5mm thickness between 2 sheets of greaseproof paper, cut with 5cm round cutter. Put on trays, brush with milk, sprinkle with Hundreds and Thousands. Cook in moderate oven 8-10 minutes. Allow to cool on trays before removing