To prepare crust, lightly spoon flour into a dry measuring cup, and level with a knife. Combine 1/4 cup flour, water, and vinegar in a small bowl, and stir with a whisk until well-blended to create a slurry. Set aside. Combine 3/4 cup flour and salt in a large bowl, and cut in shortening with a pastry blender or 2 knives until mixture resembles coarse meal. Add slurry to flour mixture, and toss with a fork until moist. Press the mixture gently into a 4-inch circle on heavy-duty plastic wrap; cover with additional plastic wrap. Chill 15 minutes.
Preheat oven to 400°.
To prepare filling, heat oil in a large nonstick skillet over medium-high heat. Add curry; cook 2 minutes. Add potato, onion, bell pepper, garlic, and chicken; stir-fry 3 minutes. Add broth and next 5 ingredients (broth through black pepper); bring to a boil. Cover, reduce heat, and simmer 5 minutes or until chicken is done. Combine cornstarch and water in a small bowl. Stir in cornstarch mixture and cream cheese; cook 1 minute or until cream cheese is melted.
Spoon the filling into a round 2-quart casserole coated with cooking spray. Roll the crust into an 11-inch circle, and place over mixture. Cut 6 slits in top of the dough to allow steam to escape. Bake at 400° for 30 minutes or until golden brown and bubbly around the edges. Let stand 10 minutes.
Note: You can also make this in an 11 x 7-inch baking dish. When you prepare the crust, press the dough into a 6 x 4-inch rectangle, and chill. Roll dough into an 11 x 7-inch rectangle and place over the filling.