To start making the samosa dough or pastry, mix together flour and salt and add oil.
Rub the oil with the flour till it resembles bread crumbs. Start by adding 1/2 cup water and knead it into a firm dough.
You may need a few extra teaspoons of water but add as you go. The consistency of the dough should be firm and smooth.
Cover the dough with a damp cloth and set aside while you make the filling.
Filling:
Heat oil in a pan add jeera and coriander seeds (crushed) . Fry the spices till aromatic but be careful not to burn them.
Add ginger and green chillies and stir fry for a minute or two. Add the remaining spices, now add mashed boiled potatoes and salt.
Give it one more good mix and then set the mixture aside to cool.
Take a lime sized bowl of dough, roll it between your palms till smooth and dust it with flour.
Wrapping the samosas:
Roll it out into a circle which is less than 1 mm thickness.
Cut the rolled dough in half. Pick up one half and brush it with a little water along the straight edge of the pastry.
Now take one edge of the straight side, and place it on the other edge of the straight side in such a way that the dough forms into a cone.
Pinch the corner of the cone so that its sealed. Place a tablespoon and a half of the filling in the cone, making sure to fill it only 3/4th of the way.
Brush the inside of the unfilled dough with a little water and seal it by pinching the edge together.
Repeat till all the dough is used up. Place the samosas on a greased tray making sure they don't touch each either and cover them with a damp cloth.
Frying the samosas:
Heat oil in a pan. To test if the oil is hot enough, add a tiny piece of dough to the oil and if it bubbles and floats on the surface, your oil is ready for frying.
Add the samosas to the oil making sure not to overcrowd the pan, and reduce the flame to a simmer.
Fry the samosas on a low flame till golden brown on either side. Its important to fry them on a low flame, or the pastry would be raw from the inside and golden brown on the outside. Take them out on a plate lined with paper to absorb any extra oil and serve them immediately with ketchup, coriander chutney or tamarind chutney.