In large bowl, stir together flour and salt. Add oil and stir until well blended. Gradually add enough of the water, stirring with fork, to make a firm dough. Turn out onto floured surface. Knead 5 minutes until smooth; cover and let rest for 30 minutes.
Peel and cut potatoes into 1/4 inch (5 mm) cubes; set aside.
Heat large skillet over medium heat. Add mustard seeds to pan and cook, stirring, for about 5 minutes or until seeds turn gray and start to pop. Remove and set aside.
Heat oil in pan and add onions, ginger and curry paste; cook, stirring, for 5 minutes or until softened. Add potatoes and cook for 2 minutes.
Pour in stock, salt and lemon juice; bring to boil reduce heat, cover and simmer for 10 minutes or until potatoes are tender and liquid is almost absorbed.
Stir in peas and chopped coriander; remove from heat; set aside.
Divide pastry into 10 balls. Working with one at a time and keeping the remaining covered, roll each into a 7-inch circle. Cut the circle in half and brush edge with water. Add a rounded tablespoonful (15 mL) filling and fold the pastry to form a cone. Press the straight edges to seal. Fold the rounded edges together and crimp to seal. Repeat with remaining dough and filling.
In large shallow saucepan, heat oil to 350°F or until a cube of bread browns in
30 seconds. Cook 2 to 3 samosas at a time for 4 to 5 minutes, turning once, until golden. Drain on paper towels.