Combine 4 cups flour, salt and 1/2 cup shortening. Mix in 1-1/2 cups water (1/2 cup at a time), until soft dough forms. On a floured surface, roll into a large rectangle. Spread dough with 1/4 cup shortening and sprinkle with 1 TBS flour. Fold dough onto itself in three layers (similar to a letter). Spread with remaining shortening, sprinkle with flour and fold into thirds, making a square. Wrap dough in plastic and chill overnight.
In large pot over low heat, combine 4 TBS oil and 4 TBS flour and stir to make a roux. Add onion and cook until golden. Add celery and green pepper. In large skillet over medium-high heat, sauté chicken pieces in 4 TBS oil until golden brown. Add chicken to pot with vegetables and cover with water. Bring to a boil; reduce heat and cover. Simmer for one hour or until chicken is tender. Remove chicken and place in refrigerator to cool. In small skillet, sauté chopped mushrooms in 2 TBS butter until golden and liquid evaporates. Add sautéed mushrooms and parsley to liquid from above. Reduce liquid (at a rolling simmer) to one-half (approximately 30-45 minutes). Liquid should be reasonably thick before adding chicken. Pick meat from chicken, shred and add to liquid along with pepper flakes.
Preheat oven to 375 degrees. Roll out dough on floured surface and cut into 20 circles, 5" in diameter. Leaving a 1/2" edge uncovered, fill 10 circles equally with chicken mixture (drained with slotted spoon) and add several tablespoons of liquid over chicken. Brush edges of dough with egg wash and place equal size circle of dough on top; seal edges with a fork. Brush top of pie with egg wash. Bake at 375 degrees for 30 minutes, or until golden. 10 servings.
To freeze: Fill pastry with chicken, and small amount of liquid, cover with dough and brush with egg wash. Freeze on cookie sheets until firm and place in plastic zipper bags. Bake at 375 degrees for 40 minutes, or until golden.