Combine currants and hot water in 2-cup glass measure; let stand 10 minutes, until currants are plump and water is a light caramel color. Remove currants with slotted spoon to cup. Add enough water to return currant liquid to 3/4 cup.
Meanwhile, sprinkle yeast over warm water in bowl; let stand 5 minutes, until creamy. Add yeast to currant liquid; stir in honey and butter.
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.
Grease a large cookie sheet; sprinkle with cornmeal. Punch down dough; transfer to lightly floured board. Divide dough into 16 equal pieces. Shape each piece into a ball. Arrange balls about 1-1/2 inches apart in four rows on prepared sheet. Cover and let rise until almost doubled in bulk, 45 minutes to 1 hour.
Arrange oven rack in lower third of oven. Heat oven to 425 degree F. Brush roll tops with egg white. Bake 18 to 20 minutes, until golden brown. Cool on wire rack. Serve warm or at room temperature. Makes 16 rolls.