Wash and peel potatoes. Cut them into big dices. In a pressure cooker, pour about 1 glass of water. Place a colander with potato dices in it. Wait for 1 whistle on medium to high heat. 

Mix all dry ingredients except soda. Add oil and then water little by little. Make it quite thick, but pouring consistancy (like cake batter) as it gets a bit thin after adding soda. Keep aside.

Add soda just at the time of use and mix briskly with a fork.

For seasoning, take 1 tbsp oil in a pan. Crackle mustard seeds. Add hing, lime, and chili-ginger paste. Fry a little and then add sultanas and haldi. Mix and remove from heat when oil oozes.

Lightly mashed potatoes with a fork or a masher. Pour seasoning, lemon, sugar, coriander leaves, and garam masala. Mix well. Adjust seasoning to garam masala, sugar and lemon flavor to stand out distinctly.

Make small to medium size balls. Keep aside. Add soda in the batter and beat using a fork in the same direction till it's light.

Add a little water if required. It should be a little loose ribbon consistency (see in the picture that the ribbons are formed, bit a little smaller and thinner than before)

Heat oil in a deep pan. The level of the oil should be as much as can emerge the potato balls fully. Heat the oil till medium to hot. Deep potato balls into chana batter and cover it with batter all around. Gently pick it with a fork, drain out extra batter by rubbing the fork at the edge of the bowl.

Slowly drop it in the oil. Do not stir them until they are a bit cooked all around. Keep stirring and fry for 3-5 mins or until it gets the right color. Then take them out on a kitchen towel.

Serve hot with green chutney and sweet chutney (ketchup doesn't go well with it).

Cook potatoes well. A little less cooking will make the stuffing starchy and overcooking will make it difficult to handle. It is highly advisable to use non-starchy potatoes. Thin-skinned or dark pink skinned potatoes are ideal for this recipe.

Make chana batter at least 15 min before time so as to give it enough time to settle and soothe. The RI consistency of the batter is very important. It should be just a little thinner than cake batter. Too thick a batter will make the outer layer of vadas quite thick and hard whereas thin and runny batter will give a layer that barely covers the stuffing.

Both the type will not taste nice. We are looking for the consistency of the batter that makes a smooth, meat, and thin layer, not thick and spongy.

There must be a good balance of chilies, sugar, and lemon. The ideal stuffing tastes outstandingly sweet-tangy-spicy with a mild flavor of lime and garam masala. My experience so far taught me that it is better to add seasoning in the mashed potatoes and not the other way round. Mixing them off the flame gives it a better taste. 6.  use a fork to drop vadas in the oil.