How to Make It
Lightly spoon 1 cup bread flour and whole-wheat flour into dry measuring cups; level with a knife.
Combine with sponge and next 4 ingredients (sponge through salt) in a food processor; process until dough forms a ball. Process dough 1 additional minute. Turn dough out onto a lightly floured surface, and knead in currants, 2 tablespoons bread flour, and rosemary. Shape into a 9-inch round loaf, and place loaf on a baking sheet coated with cooking spray. Cover and let rise in a warm place (85°), free from drafts, 45 minutes or until doubled in bulk.
Preheat oven to 375°.
Uncover loaf, and make a tic-tac-toe slash 1/4-inch deep across top of loaf using a sharp knife. Bake at 375° for 40 minutes or until loaf sounds hollow when tapped. Remove from pan, and cool on a wire rack.