DAY ONE: In large warmed bowl, combine starter, molasses, potato water and whole-wheat flour. Stir well, cover with plastic and a heavy towel and let rise in warm place overnight or at least 12 hrs.
DAY TWO: Bring broth to boil, add cornmeal and, stirring constantly, cook 2 mins. Remove from heat, stir in potatoes and cool to lukewarm; add to starter mixture. Sprinkle yeast over lukewarm water, stir to dissolve an let stand until foamy. Add to starter mixture with salt, butter and spices. Beating constantly, add rye meal, rye flour and white flour. Dough will be sticky and heavy. Turn out onto floured board and, adding additional flour as needed to prevent sticking, knead 8 mins. If dough is still sticky after 5 mins, lightly oil board and hands and finish kneading. Dough will be slightly sticky to hands but should not stick to board. Form into smooth ball, place in oiled bowl, turn to coat all surfaces, cover with towel and let rise in warm place 1 hr or until double in bulk. Punch down and turn out onto floured board; knead for 20 turns. Cover with towel and let rest 5-10 mins. Divide into 2 equal portions and form each into a long loaf. Place side by side on large greased baking sheet. With sharp razor, cut 3 slashes from end to end 1/2 in deep. Brush evenly with egg white wash, being carful not to spill onto baking sheet, and sprinkle generously with poppy seeds. Let rise, uncovered, in warm place 45 mins or until almost double in size. Bake in oven preheated to 400 20 mins; reduce heat to 375 and bake 30 mins longer or until bread tests done. to give top a shiny dark look, place under broiler and, being carful of scorching, broil until dark. Transfer to wire rack and cool.