In a medium saucepan, combine split peas and water. Bring them to a boil, reduce heat, cover. Simmer until peas are tender, about 35 to 45 minutes. Drain peas and set aside.
Boil potatoes with 1 teaspoon salt until they are tender. Drain and mash potatoes.
Combine flour and salt in a medium-sized bowl. Make a well in the center and add yogurt and canola oil. Mix ingredients until they form a ball.
Knead dough on a lightly floured surface until it is smooth- about 2 to 3 minutes. Cover dough, and set aside for 30 minutes.
Heat 1 tablespoon canola oil in a heavy skillet. Add onions, stirring frequently until they are translucent. Add ginger and continue stirring for another minute. Add coriander, garam masala and salt and cook, stirring for thirty seconds. Mix in potatoes and peas. Set filling aside.
On lightly floured surface, roll out the dough into a rectangle measuring about 12 x 18 inches. Cut dough into 3-inch squares.
Place 1 tablespoon of filling on each square. Use your fingers to moisten edges of dough with water, and fold dough diagonally in half to make a triangle. Press edges firmly together to seal in the filling.
Heat 1 inch oil in a heavy skillet until it is hot but not smoking, about 350° to 380°. Fry samosas until golden, turning once. Drain samosas on paper towels, and keep them hot.
Transfer samosas to a heated serving dish. Serve with chutney or ketchup.