Three days in advance: In a bowl, combine the yeast with the lukewarm water. Add the 2 cups flour and blend. Pour the starter into a container and seal tightly. Allow starter to sit at room temperature for 2 days. Then place in the refrigerator for 1 day.

One day in advance: Place 1 cup of the “starter” in a bowl. Measure in the rye flour and lukewarm water. Mix together and cover with plastic wrap. Let stand overnight at room temperature.

The bread: Dissolve the yeast with ¼ cup of the lukewarm water. Stir down the dough that has been standing overnight. Add the dissolved yeast, salt, caraway seeds, poppy seeds, melted butter, and sugar. One cup at a time, add 4 cups of the flour, stirring to make a stiff dough. Turn the dough out onto a clean surface and knead for 10 to 12 minutes. Shape the dough into a ball and place in a buttered bowl. Turn the dough over to coat it with butter. Cover and place in a warm draft-free place to rise until doubled in bulk, about 2 hours.

Meanwhile, butter 2 baking sheets and generously sprinkle with cornmeal.

Punch down the dough and divide it in half. Shape each piece of dough into a free-form loaf and place it on the prepared baking sheets. Cover and let it rise for 1 hour.

Preheat the oven to 375°. Brush the loaves with the egg wash and bake for 30 minutes, or until the bread is golden and sounds hollow when the bottom is tapped.