Dissolve yeast and 1 teaspoon sugar in warm water, stirring well; let stand 5 minutes or until bubbly.
Pour scalded milk over butter in a large mixing bowl; stir until butter has melted. Cool to lukewarm (105° to 115°). Add remaining sugar, yeast mixture, salt, and 4 eggs, stirring well. Gradually add whole wheat flour, beating well. Add enough bread flour to form a stiff dough.
Turn dough out onto a floured surface; knead 10 minutes or until smooth and elastic. Place in a greased bowl, turning to grease top. Cover and let rise in a warm place (85°), free from drafts, 1 hour and 15 minutes or until doubled in bulk.
Punch dough down; turn out onto a lightly floured surface. Let rest 5 minutes. Divide dough into 3 equal portions, shaping each portion into a round loaf. Place loaves on greased baking sheets sprinkled with cornmeal. Combine egg yolk and whipping cream; mix well, and lightly brush over top of loaves. Cover and repeat rising procedure 1 hour or until doubled in bulk.
Bake at 400° for 10 minutes; reduce temperature to 350°, and bake an additional 20 minutes or until loaves sound hollow when tapped. Remove bread from baking sheets; cool on wire racks.