1Put sweet potato into a saucepan with enough water to cover completely; bring to a boil. Reduce heat to medium-low and simmer until just tender, about 15 minutes; drain.
2Preheat oven to 400 degrees F (200 degrees C).
3Combine water, onion, and garlic in a saucepan; bring to a boil, reduce heat to low, and cook at a simmer until onion softens, about 5 minutes.
4Stir gravy mix, cumin, cinnamon, curry powder, ginger, black pepper, turmeric, and salt into the water; add leftover pot roast, sweet potatoes, peas, and corn. Cook the mixture, stirring occasionally, until heated through, about 5 minutes; pour into the frozen pie crust. Sprinkle feta cheese over the filling.
5Bake in preheated oven until crust is golden brown around edges, about 25 minutes.
Footnotes
Tip
Aluminum foil helps keep food moist, ensures it cooks evenly, keeps leftovers fresh, and makes clean-up easy.