01In large bowl, whisk together flour and 1/4 teaspoon salt. Add olive oil and, using fingertips, blend until mixture resembles coarse meal. Add 1/4 cup water and stir with fork just until mixture comes together.
02Turn dough out onto lightly floured surface and knead until smooth and elastic, about 10 minutes. Transfer to medium bowl, cover with towel, and set aside to rest for at least 30 minutes.
03In medium saucepan over moderately high heat, heat oil. Add onion, garlic, ginger, 1/4 teaspoon salt, and 1/4 teaspoon pepper and sauté until softened, about 4 minutes. Add lamb and sauté until browned, about 8 minutes.
04Stir in curry powder and cumin and sauté 2 minutes. Stir in wine and cook, stirring frequently, until liquid is almost completely absorbed, about 2 minutes. Stir in chicken stock, reduce heat to low, cover, and simmer until lamb is tender, about 30 minutes. (Lamb can be cooked ahead and refrigerated, covered, up to 24 hours.)
05While lamb is cooking, in medium saucepan over moderately high heat, combine potatoes and water to cover by 1 inch. Bring to boil, then reduce heat to moderately low and simmer, uncovered, until tender, about 15 minutes. Drain in colander, then transfer to large bowl and, using fork, gently mash. Stir in remaining 1/4 teaspoon salt and 1/4 teaspoon pepper.
06In small saucepan over moderately high heat, boil peas in salted water until tender, about 1 minute for frozen and 5 minutes for fresh. Drain, rinse under cold running water, and drain again. Transfer to bowl with potatoes.
07When lamb is tender, transfer to food processor and pulse until finely chopped but not puréed. Transfer to bowl with potatoes and peas. Add cilantro and fold mixture to combine. (Filling can be made ahead and refrigerated, covered, up to 8 hours.)
08Divide dough into 12 equal pieces and roll each piece into ball.
09On floured surface, using rolling pin, roll out 1 ball to 6-inch-diameter circle. Spoon about 2 tablespoons filling into center. Moisten finger with cold water and run around inside edge of dough circle.
10Imagining circle as face of clock, grasp edge at 2 o'clock and pull up over center of filling. Work around edge, pulling up at 4, 6, 8, 10, and 12 o'clock positions and crimping edges where they come together to seal, to form bundle resembling a truncated pyramid. Transfer to large baking sheet.
11Repeat to form remaining samosas. (Samosas can be formed ahead and refrigerated on baking sheet, loosely covered with plastic wrap, up to 2 hours.)
12In heavy 6-quart pot over moderately high heat, heat 4 inches of oil until thermometer registers 350°F. Working in batches of 3 and returning oil to 350°F between batches, fry samosas until golden brown, 4 to 5 minutes. Transfer to paper towel–lined platter to drain.