1. Fit 1 piecrust into a 9-inch deep-dish pieplate according to package directions; trim dough around edges of pieplate.
2. Place remaining piecrust on a lightly floured surface; cut desired shapes with a decorative 1-inch cookie cutter. Brush edge of piecrust in pieplate with beaten egg white; gently press dough shapes onto edge of piecrust. Pierce bottom and sides with a fork.
3. Line piecrust with parchment paper or aluminum foil; fill piecrust with pie weights or dried beans.
4. Bake at 400° for 10 minutes. Remove weights and parchment paper; bake 5 more minutes, and set aside. Reduce oven temperature to 350°.
5. Cook bacon in a large skillet over medium-high heat until crisp. Remove bacon, and drain on paper towels, reserving 2 tsp. drippings in pan. Crumble bacon, and set aside.
6. Sauté chopped onion and mushrooms in hot drippings 3 to 4 minutes or until tender.
7. Stir together bacon, onion mixture, half-and-half, and next 4 ingredients in a large bowl. Combine cheese and flour; add to bacon mixture, stirring until blended. Pour mixture into crust.
8. Bake at 350° for 45 to 50 minutes or until a wooden pick inserted in center comes out clean. (Shield edges with aluminum foil to prevent excess browning, if necessary.) Let stand 10 minutes before serving.