1In large bowl, mix 1 1/2 cups of the all-purpose flour, the mashed potatoes (dry), brown sugar, salt, 3/4 teaspoon caraway seed and the yeast. In 1-quart saucepan, heat buttermilk, water and oil over medium heat, stirring frequently, until very warm (120°F to 130°F); stir into potato mixture until blended. Stir in rye flour and enough remaining all-purpose flour to make dough easy to handle.
2Place dough on lightly floured surface; gently roll in flour to coat. Knead about 8 minutes or until smooth and springy. Grease large bowl with shortening or cooking spray. Place dough in bowl, turning dough to grease all sides. Cover; let rise in warm place about 1 hour or until dough has doubled in size. (If using fast-acting yeast, do not let rise 1 hour; cover and let rest on floured surface 10 minutes.)
3Grease large cookie sheet with shortening or cooking spray; sprinkle with cornmeal. Roll dough into rope, about 3 inches thick and 25 inches long. Curl dough into coil shape; tuck ends under. Place on cookie sheet. Cover; let rise in warm place 30 to 45 minutes or until dough has doubled in size.
4Heat oven to 400°F. Brush water over dough; sprinkle with cornmeal and additional caraway seed. Bake 23 to 28 minutes or until loaf is golden brown and sounds hollow when tapped. Remove from cookie sheet to cooling rack; cool.