Rinse the chilies with fresh water and pat dry with a clean kitchen towel. With a paring knife, make a slit in each chili pepper, length wise, making sure not to cut all the way. Carefully remove the seeds and veins from inside the pepper. Repeat until all the chilies are slit and their innards removed.
Set a heavy bottomed skillet on medium high heat and add a tablespoon of oil to it. Once the oil is hot and shimmering, add the cumin seeds and chopped green chill. Let the cumin seeds splutter and then add turmeric, coriander and red chili powder.
Add the boiled and mashed potatoes to the skillet, sprinkle salt, amchur powder and garam masala. Give everything a big mix and check for seasonings. Adjust if required, turn the heat off and set aside to cool.
While the potatoes are cooling, get the batter ready. Take a deep mixing bowl and add the besan along with ajwain, salt, turmeric and baking soda. Whisk to combine. Slowly start adding the water while whisking until a smooth batter forms. The batter should be medium consistency – neither very thick (think pancake) nor too thin (think crepe), so somewhere in-between a pancake and crepe batter consistency. I hope this makes sense.
Take about 2 teaspoons of potato mixture and start stuffing the chili peppers. The amount of potato mixture you use for each chili will depend on the size of the peppers you are using. The potato mixture should be completely contained in the pepper and not over stuffed.
Set a kadaahi or small skillet on high heat and oil for deep-frying. Heat the oil (if you have a candy thermometer, it should read close to 350 degrees F. While the oil is heating up finish stuffing all the peppers. If you do not have a candy thermometer, a good way to check the oil temperature is by dropping a drop of batter in the oil. The batter should sink and then slowly rise to the top of the oil.
Dip each stuffed pepper in the batter, one at a time, and carefully drop into the hot oil. Fry till golden. Remove the pakoras out on a cookie sheet or tray lined with paper towels. Sprinkle chaat masala and serve hot with ketchup or chutney.