1. For dough, mix flour and salt and rub in shortening, as if you were making pie dough. Pour in 5-6 tablespoons cold water and mix until it becomes kneadable. If needed, add the rest of the water.
2. Knead for about 10 minutes until silky smooth, let rest for 1/2 hour. For filling, heat oil and add onions, ginger and coriander. Sauté just until onions start to brown. Boil potatoes until tender, and drain. Cook carrots until tender.
3. Softly mash potatoes so that there are still some pieces. Stir in carrots, peas, and potatoes into onions and heat slightly. Form 6" circles with dough and place filling into center. Moisten edges and seal in a crescent shape.
4. Let dry uncovered for about a 1/2 hour. Heat the oil to 350 degrees F and fry samosas in small batches until browned and heated through.