In a large bowl, combine the flour, salt, and oil/ghee. Mix well and gradually add water. Knead into a smooth dough and cover it with a damp cloth. Set aside for at least 30 minutes.
Heat oil in a pan, add cumin and coriander seeds. Add chopped ginger, green chillies, mashed potatoes, peas, turmeric powder, red chilli powder, garam masala, and salt. Mix everything well and cook for 2-3 minutes.
Divide the dough into small balls. Roll each ball into a thin circle and cut the circle in half. Take one semi-circle and fold it into a cone shape, sealing the edge with a little water. Fill the cone with 1-2 tablespoons of the potato filling.
Seal the open edge by pinching the dough together, forming a triangle shape. Heat oil in a deep pan on medium flame. Gently slide a few samosas into the hot oil. Fry the samosas until they are golden brown and crisp.
Remove the samosas and drain on paper towels to remove excess oil. Serve the hot samosas with mint chutney, tamarind chutney, or ketchup.