Cut onion,garlic,ginger(a very little one) into very small pieces and grind this as a paste.Now, heat oil in a pan and keep saute this paste to get rid of the raw smell and make it into a gravy. Boil potatoes and peas separately. Peel off the potatoes and cut into very small cubes. Now add this potatoes and peas to the above gravy.To this add garam masala/channa masala and salt to taste. Garnish with coriander and onion pieces. ( can add a drop of dilute tamarind paste if necessary).