Soak Daal overnight (or at least 8 hours) with a pinch of salt and wash thoroughly after that.
Grind daal along with chilies, ginger paste, salt and fennel seeds into a smooth paste by using little water.
Heat mustard oil in a pan and temper with Hing / asafoetida and add Daal paste and sauté the mixture for around 10 minutes in medium flame till the mixture turns dry and a bit sticky. Remove the stuffing from heat and keep the mixture aside.
Take the flour in a big bowl and mix with salt and 1 tablespoon oil properly. Add lukewarm water and knead it for sometimes to make a non-sticky dough. Cover the dough with a wet cloth/cling film and give it 15 minutes of standing time.
Knead the dough once again and divide the dough into 20 small balls and keep them aside.
Divide the stuffing into 20 equal portions and make small balls.
Take one flour ball and roll with the help of your hand and flatten it a bit and then put one stuffing ball in the middle and seal the flour ball by bringing the sides together. Repeat the process with rest of the flour balls.
Heat sufficient oil in a big pan for deep frying.
Take one stuffed ball and roll out into around 3” disk without puncturing it.
Check the oil and fry the kachori till it turns golden brown under medium heat and repeat the process with rest of the kachoris.
Best partner of these kachoris is Aloo Cholar Daal er Tarkari.