1. Put chopped butter into large bowl and pour boiling water over it. Stir until butter is dissolved. Stir in sugar and salt. Stir in 1 cup evaporated milk and let mixture cool to lukewarm (about 95 degrees F). Stir yeast into lukewarm liquid. Mix in eggs and 4 cups of flour. Mix in currants, if desired. Mix in enough remaining flour to make a soft dough. Turn dough out onto floured board and knead for 5 minutes. Place dough in greased bowl. Turn dough over so that the top is lightly greased. Cover and let rise in warm, draft-free place for 1 hour. Punch down dough and knead for 3 minutes. Shape dough into 18 buns.
2. Set buns on greased baking sheets and cut a cross on the tops of each bun. Cover and let rise for about 30 minutes or until double in bulk. Bake at 450 degrees for 10 to 15 minutes.
3. Remove buns from oven and brush with melted butter. Set on rack to cool.
4. Mix confectioner’s sugar with enough evaporated milk to make a thick icing. Ice the cross you cut into each bun. Let stand until icing thickens on buns.