Place the currants or raisins in a small bowl; add vinegar. Cover and let stand while making dough. In a large mixing bowl combine 2 cups of the flour, the yeast, cardamom, and cloves. In a saucepan heat and stir 2/3 cup milk, 1/2 cup of the mascarpone cheese, 1/3 cup sugar, and salt just until warm (120 degree F to 130 degree F) and mascarpone almost melts. Add milk mixture to flour mixture along with eggs. Beat with an electric mixer on low to medium speed for 30 seconds, scraping bowl constantly. Beat on high speed for 3 minutes. Using a wooden spoon, stir in currants and vinegar and as much of the remaining flour as you can.
Turn dough out onto a lightly floured surface. Knead in enough remaining flour to make a moderately soft dough (3 to 5 minutes total). Dough will be sticky. Shape into a ball. Place in a lightly greased bowl, turning once. Cover; let rise in a warm place until double (about 1 hour). Chill dough 6 hours. (Or omit rising time; chill dough 12 to 24 hours.)
Punch dough down. Turn dough out onto a lightly floured surface. Cover; let rest 10 minutes. Meanwhile, lightly grease two baking sheets; set aside. Divide dough into 24 portions. Gently shape each portion into a ball, tucking edges under to make smooth tops. Place balls almost touching on prepared baking sheets. Cover; let rise until nearly double (1 to 1 1/2 hours). Preheat oven to 375 degree F.
Using a sharp knife, make a crisscross slash across the top of each bun. In a small bowl combine beaten egg white and water; brush over rolls. Bake for 12 to 15 minutes or until golden brown. Immediately remove buns from baking sheets. Cool slightly on wire racks. In a small bowl stir together remaining mascarpone, 1/4 cup sugar, and enough milk to make of a thick drizzling consistency. Drizzle a cross over each bun with icing. Pass additional icing for dipping. Makes 24 buns.