Add bread flour, rye flour, salt, and caraway to a bowl; whisk to combine, and set aside..
Add warm water and yeast to a stand mixer bowl; let sit 5 minutes. Add the syrup, shortening and ½ the flour mixture. Using paddle attachment, beat 2 minutes on medium speed until smooth. Add the remaining flour mixture and beat again with a spoon until smooth, about 1 to 1½ minutes. Scrape down batter from sides of bowl. Cover; let rise in warm place until doubled, about 30 minutes.
Meanwhile, grease two 5x9-inch OR 4½x8 1/2-inch loaf pans.
Beat down raised batter in about 25 strokes using a wooden spoon or dough whisk. Note that this is a thick, somewhat sticky batter. Spread evenly in prepared pans. Tap pans on table to settle the batter. Let rise only until edges of batter comes to within 1-inch of tops of large pans or reaches tops of smaller pans, about 30 minutes.
Preheat oven to 375°F.
Brush tops with water for a chewy crust, optional. Bake 40 to 50 minutes or until well-browned on sides and tops. Remove from pans and cool on rack.