In a large mixing bowl, combine all-purpose flour and salt. Gradually drizzle in vegetable oil and mix until crumbly. Slowly add enough water to form a smooth, firm dough. Knead for about 5 minutes until soft, then cover with a damp towel and let it rest for 30 minutes.

Boil the potatoes in salted water for about 15 minutes or until tender. Drain and mash. In a skillet, melt butter and sauté onion until translucent. Stir in jalapeño, ginger, and spices, cooking for another minute. Fold in the mashed potatoes, peas, and cilantro, then cool the filling.

Divide the rested dough into six portions. Roll each into a ball, flatten into a circle, and cut each circle in half. Shape one half into a cone, fill with potato mixture, and seal the open edge securely.

Heat vegetable oil to 200°F. Fry the shaped samosas in batches for about 15 minutes until golden brown and crispy.

Arrange the crispy samosas on a platter and serve hot with mint chutney or tamarind sauce.