Pulse flours, wheat germ, and salt in a large-capacity food processor. With machine on, add yeast mixture through feed tube, processing just until mixture comes together. Process 30 seconds more, until dough forms a ball. Add reserved currants and walnut pieces, pulsing until nuts are chopped. On lightly floured surface, knead dough 1 minute, until currants and nuts are evenly distributed. Place dough in lightly greased bowl; turn to grease top. Cover bowl with plastic wrap and let rise in warm draft-free place until doubled in bulk, 1-1/2 to 2 hours.