In a medium saucepan, combine split peas and water. Bring them to a boil, reduce heat, cover, and 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 the potatoes.

Meanwhile, prepare the dough. 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.

Turn the dough onto a lightly floured surface and knead it until it is smooth, about 2 to 3 minutes. Cover dough, and set it aside for 30 minutes.

Heat 1 tablespoon canola oil in a heavy skillet. Add onions and cook, stirring frequently, until they are translucent. Add ginger, and continue stirring for another minute. Add coriander, garam masala, and salt, and cook, stirring, for about a half minute more. Add potatoes and peas, and mix well. 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 scant 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, and serve them with chutney or tomato ketchup.