In a small bowl, combine flour salt and oil until mixture resembles bread crumbs. Gradually stir in water until smooth. Turn onto a lightly floured surface; knead until smooth and elastic, 6-8 minutes. Cover and let rest for 30 minutes.
Meanwhile, in a large skillet, heat oil over medium heat. Add onion and potato; cook and stir until potato is almost tender, 5-7 minutes. Add curry, garlic, ginger, cumin, coriander and cayenne; cook 2 minutes longer. Add chicken; cook and stir until chicken is no longer pink and potato is tender, 5-6 minutes. Stir in peas an salt. Remove from heat.
Divide dough into eight pieces. Roll one piece of dough into a 9×6-in. oval. Cut dough in half. Moisten straight edge with water. Bring one corner of half moon up to meet the other corner of the half moon, forming a cone. Pinch seam to seal. Fill with about 2 tablespoons chicken mixture. Moisten curved edge of dough with water; fold over top of filling and and press seam to seal. Repeat with remaining dough and filling.
In an electric skillet or deep fryer, heat oil to 375°. Add samosas, a few at a time, into hot oil. Fry until golden brown, 2-3 minutes on each side. Drain on paper towels. Serve warm with chutney if desired.