Cream butter and sugar thoroughly; add eggs, vanilla and 2 tablespoons of orange juice. Combine flour and baking powder and gradually add to creamed mixture.
Knead dough on lightly floured board for about 5 minutes. Using tablespoonfuls of dough, roll in 15cm lengths; press ends together to form rings. Let stand on ungreased baking tray at room temperature for 15 minutes.
Bake 180 C / Gas 4 for 15-17 minutes or until lightly golden.
To Make Icing: Combine icing sugar with enough orange juice to make a thin glaze. Dip each hot biscuit into glaze; cool on racks. Decorate with sugar sprinkles, if desired.