To make the filling, heat the oil in a wok or deep skillet over medium heat, until very hot. Add the coriander and cumin, and cook for 10 seconds, until aromatic (keep a cover handy to stop any seeds from flying out). Add the onion and fry over medium heat for 15 minutes. Add the ginger, potatoes, chili, peas, salt, pepper, garam masala, sugar, cilantro, and lime juice, and stir-fry for 1 minute. Adjust seasoning to taste. Remove from heat and allow to cool.
Use readymade wonton wrapper or make your own. To make the wrapper, mix the flour, salt and oil in a food processor until crumbly. Pulse and gradually add the ice water until you have dough that is almost together. Turn out onto a floured surface. Gather the dough and knead in the cumin seeds. Shape the dough into a long cylindrical shape, cover with plastic and allow to rest for 30 minutes.
Divide the dough into 10 pieces. Roll out each piece into a 6-inch oval shape. Cut each in half.
Using your wet thumb and fingers, shape each half-oval into a cone.
Fill each wrapper with 1tablespoon of filling.
Wet the top edges of the cone with water, close the cone, press together and seal. Repeat for all the dough. Place samosas on a baking sheet lined with parchment paper, separated from each other, cover with a dish towel and refrigerate until ready to cook.
To cook the samosas, heat 4cups corn oil in a wok or deep skillet over medium low heat (beware not to make the oil too hot, 330-375°F). Add 4 samosas at a time and deep-fry for 15 minutes, turning frequently until golden brown. Remove with a slotted spoon and drain on paper towels (for readymade wrapper cooking time is reduced).
To make fresh cilantro relish, puree 3cups chopped fresh cilantro leaves, ¼cup fresh mint, ¼-inch fresh ginger (peeled), 1 bird or serrano chili (seeded), 3tablespoons lime juice, 1teaspoon cumin powder, 1teaspoon salt, ½teaspoon sugar, ¼cup almonds or yogurt and ¼cup water in a food processor. Adjust seasoning to taste and transfer to a small serving bowl.
To make tamarind chutney, mix 1cup tamarind paste, ½cup pitted dates, ¼cup water, ½teaspoon salt, ¼teaspoon nutmeg, ¼teaspoon ground cumin, 1teaspoon sugar and 1 bird or serrano chili in a food processor. Adjust seasoning to taste, cover and allow to rest for 30 minutes. This chutney keeps well in the refrigerator for 1 to 2 weeks.
Arrange the hot samosas on banana leaves or on a serving platter, and serve with the cilantro relish and tamarind chutney.