Sift the flour and salt into a mixing bowl. Rub in the ghee or butter until the mixture resembles breadcrumbs. Add the water and knead thoroughly to a very smooth dough. Cover and chill while preparing the filling. Heat the oil in a pan and add the mustard seeds. Leave for a few seconds until they start to pop, then add the onion and fry until golden. Add the chillies, turmeric, ginger, and salt to taste and fry for 3 minutes; if it starts sticking to the pan add = tablespoon water and stir well. Add the peas, stir well and cook for 1minute. Stir in the lemon juice. Cool slightly. Divide the pastry into 8 pieces. Dust with flour and roll each pieces. Dust with flour and roll each piece into a thin round, then cut each round in half. Fold each half into a cone and brush the seam with water to seal. Fill the cone with a spoonful of filling (do not overfill), dampen the top edge and seal firmly. Deep-fry until crisp and golden. Serve hot or warm.