Makes 2 round loaves
In a large bowl dissolve the yeast in the warm water. Stir in the beer, molasses, lard, caraway seeds, salt, rye flour, and enough white flour until the dough becomes difficult to stir. Turn the dough out onto a floured working surface and let rest while you clean out and grease your bowl. Knead the dough, adding more white flour as necessary; it will be very tacky, but up to 3 cups of white flour in all and about 8-10 minutes of kneading should be enough. Return the dough to the greased bowl, cover with plastic wrap, and let rise until double in volume - about 2 hours.
Turn the dough out, punch it down, and form into 2 rounds. Place far apart on a greased baking sheet sprinkled with corn meal. Let rise covered with a towel until double - about 45 minutes. If you have tiles or a baking stone, heat the oven well ahead to 375 F to warm them, and to get a good crust use a device to create steam. If you don't want to bother with a steaming device, brush the loaves with cold water before they go in the oven and again two or three times during the first 10 minutes. If you have tiles or a baking stone, slip the loaves directly onto the hot surface; otherwise simply bake the loaves on the baking sheet. After 10 minutes reduce the heat to 350 F and bake another 40 minutes. Cool on racks.