Soak Black Channa with enough water for atleast 4 hours. Add them into a pressure cooker add in required water and salt to taste. Pressure cook for 2 whistles. Let the pressure cooker release pressure on its own. Drain the excess water. Let it cool down.
Add Palak leaves into luke warm water. Add 2 tablespoon of salt into it. Set it aside for 10 minutes. This process would remove the dirt and worms from the leaves if any.
Meanwhile soak basmati rice in water for 15 minutes.
Heat a pressure Cooker, add in butter and start melting butter. When it starts melting add in the contents listed under to Tamper section. When nice aroma comes out add in the onion and saute until glossy.
Add tomato and saute until mushy. Add in Ginger garlic paste and saute until it cooks well.
Grind all the ingredients listed under green paste into a paste.
Add the green paste into the biryani mixture and cook until the raw smell leaves. Add in the black channa.
Add in Garam Masala and turmeric powder. Add in the soaked rice. Add 1 Cup of coconut Milk. Give a quick stir. Close the pressure cooker and pressure cook for 2 whistles. Switch off the pressure cooker and allow it to release pressure on its own. Open the pressure cooker and fluff it off with a fork.