Wash and scrub the potatoes well to remove all dirt.
Dry and rub with oil.
Prick the potatoes on all sides a few times with a fork.
Boil the potatoes till just done.
While the boiled potatoes are still warm, halve them lengthwise.
Scoop out the inner portion very neatly, leaving 1/4" border.
Place the potato shells aside till baking time.
Chop the scooped out potato coarsely.
Keep aside for the filling.
For the sauce, in a small bowl dissolve the cornstarch in the yogurt.
Place the yoghurt mixture in a saucepan and cook on low heat.
Simmer for 5 minutes, stirring continuously.
Add a pinch of black pepper powder.
Stir in the garlic paste & salt into the cooking yogurt.
Simmer the sauce, stirring occasionally, for 2 minutes.
Keep aside.
For the filling, heat 3 tbsp oil in a pan.
Add the walnuts.
Cook over low heat, stirring, for 1-2 minutes, or until they are golden.
Remove walnuts from the pan and keep aside.
To the oil remaining in the pan add the onion.
Cook, stirring occasionally, until golden.
Add the mince.
Cook about 8-10 minutes, stirring frequently to break up the lumps.
Remove from heat.
Combine together the walnuts, meat mixture, chopped potato, cinnamon, parsley, 1/2 teaspoon salt and a pinch of pepper.
Fill the mixture in the potato shells.
Spread half of the sauce in a dish.
Arrange the potato shells over it.
Spoon the remaining yogurt sauce on top.
Bake the potatoes in a preheated oven at 230°C/450°F for 10 to 15 minutes.