Wash the chana dal with clean water twice and soak it in water for 4-5 hours. After soaking, drain out all the water and put it in a blender to grind coarsely.
Add green chilies, garlic cloves, ginger piece, cumin powder, whole black pepper, salt, turmeric powder, coriander powder, red chili powder, and carom seeds to the grinder. Add 4-5 tablespoons of water as per your need to make a coarse paste.
Take out the chana dal mixture in a bowl and add chopped green onion, chopped coriander leaves, and mix well.
Heat mustard oil in a pan over medium heat and when it is hot, carefully put the chana dal mixture into the pan using your hands. Fry until golden brown from both sides.
Remove the fried khachri from the oil and place it on a strainer to drain out excess oil.
Now make the gravy by heating some oil in a pan over medium heat. Add cumin seeds and fry for a while.
Add chopped onions, dry red chilies, and fry until the onion turns light golden brown.
Add chopped tomatoes and salt to taste. Fry the tomatoes well so that it gets cooked quickly.
Add ginger garlic paste, turmeric powder, red chili powder, coriander powder, cumin powder, and pepper powder to the pan and mix well.
Fry the spices for 4-5 minutes or until the oil starts separating from the spices. Then add water to the gravy and bring it to a boil.
Add salt to taste and cook on high flame for 8-10 minutes. Once the boil starts, lower the flame and let the gravy cook well.
After 10 minutes, add garam masala powder and mix well. If the gravy is too thick, adjust the consistency by adding hot water.
Add the dal kachri to the gravy and cover it with a lid. Cook on low flame for 8-10 minutes or until the gravy absorbs well into the kachri.
Once done, turn off the gas and garnish with chopped coriander leaves from above. Let it sit for 5 minutes before serving.