Polish Sourdough Rye Bread

From Susan Wiggs' book Winter Lodge: Pine Box Traditions. "It's a Polish wedding tradition to give a new bride a supply a starter for sourdough rye bread. I suspect it's a combination of tradition and desperation on the part of the bride. It just doesn't seem fair to add the pressure of making a good bread right out of the gate to everything else the poor girl is juggling."

• Ready In: 1 hr 35 mins
• Yields: 3 loaves

Ingredients

• 2 (1/4ounce) packages active dry yeast or 4 1⁄2 teaspoons active dry yeast, separated
• 1  tablespoon white sugar
• 2  cups warm water, 80 degrees F
• 1  slice onion
• 4  cups  rye flour
• 1  cup buttermilk, room temperature
• 1  teaspoon baking soda
• 1  tablespoon salt
• 8  cups bread flour
• 1  tablespoon caraway seed (optional)

Directions

1. The night before making the bread, in a medium-sized mixing bowl, dissolve one packet of yeast and the sugar in 2 cups of water. Let stand until creamy, about 10 minutes. Stir in the rye flour until the mixture is smooth. Add the onion slice. Cover and let stand overnight.
2. The next day, dissolve the remaining package of yeast in the buttermilk. Add the rye flour mixture, baking soda, salt, 4 cups of the bread flour and stir to combine.
3. Add the remaining 4 cups of bread flour, 1/2 cup at a time, stirring well after each addition (you may not need to add all the flour).
4. When the dough has become a smooth and coherent mass, turn it out onto a lightly floured surface and knead until smooth and supple, about 8 minutes. Sprinkle the caraway seeds on the dough and knead them in until they are evenly distributed throughout the dough.
5. Lightly oil a large mixing bowl. Place the dough in the bowl and turn to coat with the oil. Cover with a damp cloth and let rise in a warm place for about 1 hour until the volume has doubled.
6. Preheat over to 350 degrees F.
7. Turn the dough onto a lightly floured surface and divide into three pieces. Form each piece into a loaf and place in 3 lightly greased 9x5 inch bread pans. Cover and let rise until nearly double, about 1 hour.
8. Bake at 350 for about 35 minutes 0r until the loaves sound hollow when tapped.