Grease two 8 1/2 x 4 1/2 loaf pans, and line with parchment paper. Lightly crack the sugar cubes, but don't crush them--break in halves or quarters. Place them in a small bowl, and sprinkle with cinnamon, and toss lightly to dust with the cinnamon.
**By hand or mixer: Place 2 cups of flour, dry milk, yeast and salt in the mixing bowl. Pour in the hot water and add the shortening. With the mixer, beat for 2 minutes, medium speed, or beat 150 strong strokes by hand with a wooden spoon. Stir in remaining flour, 1/2 cup at a time, until a rough mass is formed.
**By processor: Attach plastic dough blade, place 3 cups flour in the work bowl, and add dry milk, yeast, salt and shortening. our in hot water. Pulse 3 or 4 times, until well blended. Add additional flour 1/4 cup at a time, until dough is no longer wet, but still soft and slightly sticky. Process until dough forms a ball, and cleans sides of bowl. Let the dough knead for an additional 50 seconds.
**Kneading, for both methods: Turn the dough onto a lightly floured surface, and knead for 2 minutes. Flatten dough, and sprinkle with 1/4 cup of the sugar mixture, fold dough over, and continue kneading. hen cubes have disappeared into the dough, add another 1/4 cup. Again work sugar in with a kneading motion. Repeat with remaining cubes. Knead for 8 minutes. The dough will take on the cinnamon color; that's fine. If the cubes poke out, push them back in, and lightly flour if the dough becomes sticky from sugar.
**First rise: Place dough in greased bowl, turn to coat, cover bowl with plastic wrap, and let rise in a warm place until dough doubles in bulk, about 45 minutes to an hour.
**Shaping: Turn the dough onto the work surface and divide with a sharp knife. Cut edges will expose sugar pockets. Carefully close these pockets, pinching seams tightly. Shape the pieces into balls, and let them rest for 3-4 minutes. Form a loaf by pressing or rolling each into an oval, about the length of the pan. Fold oval in half, pinch seam to seal, tuck under the ends, and place in the pan, seam down. Repeat with second loaf.
**Second rise: Preheat oven to 400 degrees.
Place pans in a warm place, (not the oven!) cover with parchment paper, and leave until the center of the loaf has risen to 1/2" above the top of the pan, about 45 minutes.
**Baking: If desired, cut a pattern into the top of the loaf with a sharp knife. Place the loaves in the hot oven for 15 minutes. Reduce heat to 350 degrees, and bake for an additional 40 minutes. Midway through baking, shift the bread to expose the loaves evenly to oven shifts. Carefully turn pans on their sides on a cooling rack. Tug gently on the paper lining, loosening the breads and pull them out. Allow to cool before serving.