Return bowl to mixer and knead until smooth and elastic, for about 3 more minutes. Add currants or raisins and knead until well mixed. Dough will be wet and sticky. Shape dough into ball, place in buttered dish, cover with plastic wrap and let rise overnight in the refrigerator.

Let dough sit softened for about a half-hour. Grease a large baking pan. Divide dough into 24 equal pieces. Shape each portion into a ball and place on baking pan, about 1/2 inch apart. Cover with a clean kitchen towel and let rise in a warm, draft-free place until doubled in size, about 1 1/2 hours.

When buns have risen, take a sharp knife and carefully slash buns with a cross. Brush with egg white and place in oven. Bake 10 minutes, then reduce heat to 350° F, then bake until golden brown, about 15 minutes more. Transfer to a wire rack. Whisk together glaze ingredients, and spoon over buns in a cross pattern. Serve warm.