Combine pork, beef, onion and garlic in large heated skillet. Cook, stirring often until meats lose pink color. Stir in poultry seasoning, salt, pepper, celery, sage and water. Cover. Simmer 20 minutes. Uncover, simmer 10 minutes longer. Remove from heat. Stir in mashed potatoes. Cool. Prepare pie crust mix. Divide into fourths. Put crust into 9-inch pie shell, spoon half of cooled meat mixture into shell. Fold over edges of crust. Brush with egg. Put on top crust. Trim. Brush with egg. Cut slits in middle. Repeat for second pie. Bake at 425 degrees for 15 minutes then reduce heat to 350 degrees and continue cooking for 25 minutes. Bake and freeze or serve right away. Makes two pies.