1. Preheat oven to 400°. Unroll piecrust on a lightly floured surface; roll into a 14- x 12-inch rectangle.
2. Cook bacon slices in a large skillet over medium heat 5 minutes on each side or until crisp. Remove bacon slices, reserving drippings in skillet. Crumble bacon.
3. Sauté mushrooms in hot drippings 10 minutes or until tender. Add minced garlic cloves, and sauté 1 minute.
4. Stir together soup and next 6 ingredients in a medium bowl. Stir mushroom mixture and crumbled bacon into chicken mixture. Pour into a lightly greased 11- x 7-inch baking dish. Top with piecrust; fold edges under, and crimp. Cut slits in top for steam to escape.
5. Bake at 400° for 45 minutes or until golden and bubbly. Let stand 10 minutes before serving.
*2 (12.5-oz.) cans chicken, drained, may be substituted.
Note: To make ahead, prepare recipe as directed through Step 4. Cover tightly with aluminum foil, and freeze up to 1 month. Preheat oven to 400°. Remove pie from freezer, and let stand at room temperature 30 minutes. Loosen foil, and place pie on a foil-lined baking sheet. Bake, covered, for 1 hour and 30 minutes. Uncover and bake 15 to 20 minutes or until golden and bubbly.