Soak both channa and green moong overnight and pressure cook separately for 3 whistles. You can cook potato along with this too.
In a mixing bowl, mix the flour with semolina, corn flour, salt, oil well and make a tight dough by sprinkling water little by little. Let it set for minimum 1 hr so that it will be easy to roll.
After an hour knead well to a smooth dough and divide into equal size balls say 6- depending on how big you want the kachori.
Roll into a round circles. Heat oil in a kadai and let it be hot. Drop the puri one by one , it should puff up as shown in the picture. So make sure the oil is hot enough.
After it puffs up, lower the flame to maximum low and cook both side to get a golden brown crispy puri. Make all the ingredients ready including the chutneys.
At the time of serving, you can break the puri in the middle and fill it with mashed potaotes, channa, moong and a crushed papdi. Add both the chutneys.
Beat curd smoothly with little salt and sugar. Top the kachori with generous curd, both chutneys again and sprinkle sev over and garnish with more channa and moong and coriander leaves.
You can also sprinkle the chaat masala and red chilli powders as needed.