Crisp, flaky pastry triangles filled with spiced potato and peas, folded from semicircles into cones before frying - rubbing oil into the flour until sandy before adding any water is what gives samosa dough its shatteringly flaky layers, and letting the filling cool completely is what keeps the dough from turning soggy as you fold it.
1.Mix the flour and 1/2 tsp salt in a bowl, then rub in the 1/4 cup oil with your fingertips until the mixture looks sandy and holds together when pressed - this oil-rubbing step is what creates the flaky layers in the fried pastry.
2.Gradually add the water and knead into a firm, smooth dough. Cover and let rest for 20-30 minutes.
3.Heat a little oil in a pan and add the cumin seeds. Once they sizzle, add the ginger and green chili, then the boiled potatoes, peas, coriander powder, and garam masala. Cook for 5 minutes, mashing the potatoes slightly, then stir in the cilantro, lemon juice, and salt. Let the filling cool completely before using - warm filling makes the dough soggy and hard to seal.
4.Divide the dough into 6 balls, roll each into a thin oval, and cut in half to make two semicircles.
Take one semicircle, wet the straight edge with water, and fold it into a cone, pressing the seam to seal.
6.Fill the cone with 2 tablespoons of the cooled potato filling, then wet the top edge and pinch it closed, pressing firmly to seal completely - don't overstuff, or the seam will burst open while frying.
7.Heat the 4 cups of oil to 325°F and fry the samosas in batches for 8-10 minutes, until light golden, then increase the heat to 375°F and fry for another 2-3 minutes until deep golden and crisp - this two-stage frying is what cooks the pastry through without burning the outside.
8.Drain on paper towels and serve hot with chutney.