In a small bowl, stir together yeast and warm water.
In a large bowl, combine brown sugar, oats, lard, molasses, caraway seed, and salt. Pour boiling water over mixture. Stir until combined. When mixture cools to 105 degree F to 115 degree F, stir in yeast mixture. Beat in 2 cups of the all-purpose flour. Stir in the rye flour and as much of the remaining all-purpose flour as you can with a wooden spoon.
Turn out onto a lightly floured surface. Knead in enough of the remaining all-purpose flour to make a stiff dough that's smooth and elastic (8 to 10 minutes total). Shape into a ball. Place in a greased bowl; turn dough to grease surface. Cover and let rise in a warm place until doubled (about 1 hour).
Punch dough down. Shape into 2 round loaves. Place on a greased baking sheet; flatten to 6-inch rounds. Cover and let rise until doubled (about 1 hour).
Bake in a 375 degree F oven for 35 to 40 minutes or until bread sounds hollow when tapped. Remove from baking sheet immediately. Let cool on a wire rack. Makes 2 loaves (24 servings).