In a large mixer bowl combine 3 1/4 cups of the flour and the yeast.
In a saucepan heat the 2 cups milk, sugar, butter, and salt just till warm (115° to 120°) and butter or margarine is almost melted; stir constantly.
Add to flour mixture; add the 2 eggs.
Beat at low speed of electric mixer for 1/2 minute, scraping sides of bowl constantly.
Beat 3 minutes at high speed.
Stir in currants and shredded orange peel.
Stir in as much of the remaining flour as you can mix in with a spoon.
Turn dough out onto a lightly floured surface.
Knead in enough of the remaining flour to make a moderately soft dough that is smooth and elastic (3 to 5 minutes total).
Shape into a ball.
Place in a lightly greased bowl; turn once to grease surface.
Cover; let rise in a warm place till double (about 1 1/2 hours).
Punch dough down; turn out onto a lightly floured surface.
Cover; let rest 10 minutes.
Divide dough into 36 pieces; form each piece into a smooth ball.
Place on a greased baking sheet 2 inches apart.
Cover; let rise till nearly double (30 to 45 minutes).
With a sharp knife cut a shallow cross in each; brush tops with the beaten egg.
Bake in a 375° oven for 12 to 15 minutes or till golden.
Cool slightly.
Meanwhile, combine powdered sugar, vanilla, and enough milk (about 4 teaspoons) to make of piping consistency.
Pipe crosses on tops of buns.