First, prepare the filling
Heat the oil, then add the onions and fry till soft. Add the ginger, garlic pastes followed by the capsicum. Cook for a minute, then add the mince and the turmeric and cumin powders, plus salt. Once you've broken all the lumps, add the potato cubes and green chillies. Cook until the mince is almost dry, then add the lemon juice and coriander leaves. Finally when mince is completely dry, sprinkle the garam masala and set aside to cool.
In the meantime, take 1 egg, beat it well and set it aside. Then take an onion, peel it and cut it in half lengthwise. Slice each section into thin half-slices (soften these by sprinkling salt over the onion slices, leaving them for about 15 minutes, then washing them thoroughly and draining out all the water). Set aside.
Next, prepare the dough
Put all the dough ingredients in a bowl and knead into a soft pliable dough. Immediately, divide the dough into 4 equal-sized balls. Roll each ball out to about 7 inches diameter (it will be thin but that's fine).
Grease two pie-plates or any round pan, even a cake pan will do.
Place one rolled out chapati in each pan, this will be the base of your pies. Then divide the mince between the two pies and pour it over the bases. Next, take the beaten egg and divide it between the two pies by drizzling it on each pie very neatly all over the filling. Sprinkle the onion half-rings all over the top of the filling, then add a dash of black pepper powder over everything.
Cover each of the pies with the remaining rolled out chapatis/rounds. Press the edges with a fork or your fingers, to seal well. Now using a blunt knife, make marks dividing the pie into 8. Don't cut through, just lightly form the pattern.
Cover the dishes and set aside to rise for about an hour. Apply egg-wash on the pies and sprinkle sesame seeds if desired.
Bake in a preheated oven at 180 degrees until tops are golden.
Cut the sections through following the marks you made previously. This time use a sharp knife to get clean cuts. Serve!! :)