1. Combine warm water, honey, and yeast in a large liquid measuring cup; stir until yeast dissolves. Let stand until foamy, about 5 minutes.

2. In a large bowl, whisk 1 pound 5 ounces (about 4 cups) bread flour with whole-wheat flour, wheat germ, and salt. Make a well in the center. Pour in yeast mixture, and stir with a wooden spoon, gradually drawing in dry ingredients until combined.

3. Turn out dough onto a lightly floured work surface. Gently knead in remaining 3 ounces (about 1/2 cup) bread flour a little at a time until dough is smooth and elastic, 10 to 15 minutes. Place in a lightly oiled bowl; cover with lightly oiled plastic wrap. Let rise in a warm place until doubled in bulk, 1 to 1 1/2 hours.

4. Preheat oven to 400 degrees with rack in center. Brush two 9-by-5-inch loaf pans with oil. Punch down dough with your fist then turn it out onto a lightly floured work surface. Divide dough in half. Flatten one half into an oval approximately the length of the pan, and roll up lengthwise, gently pressing as you go to form a tight log. Place the log, seam side down, into a prepared pan. Repeat with remaining dough. Cover loaf pans with oiled plastic wrap. Let rise in a warm place until doubled in bulk, 30 to 45 minutes.

5. Using a lame or a razor blade, slash loaves down the center in one quick, even motion. In a small bowl, beat the egg yolk with the heavy cream; brush over the tops of the loaves.

6. Bake, rotating pans halfway through, until bread is deep golden brown, 50 to 60 minutes. (If tops are browning too quickly during the last 30 minutes of baking, tent with aluminum foil.) Transfer pans to a wire rack, and let cool 5 minutes. Turn out the loaves onto the rack to cool completely before serving.