Heat butermilk to lukewarm. Remove from heat. Add yeast to water in large bowl; let stand 5 minutes. Stir; add 1/2 the flour, buttermilk, sugar and salt. Beat about 100 strokes, or until smooth. Add more flour a little at a time with shortening. Mix in first with a spoon; then turn onto floured board and continue working the flour until the dough is quite stiff. Cover let rest for 10 minutes. Knead until smooth. Place in lightly greased bowl, twirling dough to cover all sides. Cover; let rise in warm place until double, about 1 hour. Dent will remain when finger is pressed inside. Punch dough down; let rest 15 minutes. divide dough into 2 parts. To shape loaf: Pat 1/2 dough into 6x12 inch rectangle. Starting at wide side, roll up tightly. Pinch edges of dough into roll; turn seam side to bottom. Taper ends by placing palms on sides of each piece of dough. Roll back and forth on board. Sprinkle cornmeal on cookie sheet. place loaves seam side down, 3 inches apart on baking sheet. Let rise in warm place until almost doubled, about 45 minutes. Make 4 diagonal slashes 1/4 inch deep on top each loaf. Brush with warm water. Just before baking brush loaves again with warm water. bake in preheated oven at 400 degrees for 45 minutes. Remove and cool on rack.