Scald the milk, then add sugar, salt and butter; cool to lukewarm.
Sprinkle yeast on the warm water; stir to dissolve.
Add eggs, yeast and 1 cup flour to the milk mixture; beat with electric mixer at medium speed about 2 minutes, occasionally scraping the bowl. Stir in currants and enough remaining flour, a little at a time, to make a soft dough that is easy to handle. Beat well. Place in lightly greased bowl; turn dough over to grease the top. Cover and let rise until doubled, about 1½ hours. Punch down. Turn onto a lightly floured surface.
Roll or pat to ½" thickness. Cut in rounds with a 2½" biscuit cutter; shape cutouts in buns. Place about 1½" apart on a greased baking sheet. Cover and let rise until doubled, about 1 hour.
With a very sharp knife, cut a shallow cross on the top of each bun. Brush tops with unbeaten egg white mixed with cold water.
Bake at 375° for 15 minutes, or until golden brown. Cool on wire racks about 5 minutes. Then, with top of knife or teaspoon, fill in crosses on buns with the White Frosting. Best served warm.