Skin chicken. In a 4-quart Dutch oven combine chicken, 3 cups water, the onion, salt, sage, pepper, and bay leaf. Bring to boiling; reduce heat. Simmer, covered, for 25 minutes. Add celery, carrots, and mushrooms. Return mixture to boiling; reduce heat. Simmer, covered, about 10 minutes more or until vegetables are tender and chicken is no longer pink (170 degrees F for breasts, 180 degrees F for thighs and drumsticks). Discard bay leaf. Using tongs, rearrange the chicken pieces so they rest on top of the vegetables.

Meanwhile, prepare Dumplings. Spoon dumpling batter into 6 mounds on top of the chicken. (Do not spoon batter into the liquid.) Return to boiling; reduce heat. Simmer, covered, for 12 to 15 minutes or until a wooden toothpick inserted into a dumpling comes out clean. Do not lift cover while simmering. With a slotted spoon transfer chicken, dumplings, and vegetables to a serving platter; keep warm.

For gravy, pour 2 cups cooking liquid into a large measuring cup. Skim fat from liquid; discard fat. Pour liquid into the Dutch oven. Stir the 1/2 cup cold water into the flour; stir into the liquid in Dutch oven. Cook and stir over medium heat until mixture is thickened and bubbly. Cook and stir for 1 minute more. Serve gravy over chicken, vegetables, and dumplings. Makes 6 servings.

Dumplings: In a medium bowl combine 1 cup all-purpose flour, 1 teaspoon baking powder, and 1/2 teaspoon salt. Cut in 2 tablespoons shortening until mixture resembles coarse crumbs. Add 1/2 cup buttermilk, stirring just until moistened.