Soak the both the rajma and urad dal overnight if you are making this in the morning.
If you are making dal makhani in the evening, then soak the dals in the morning.
In a pressure cooker, add all the ingredients including the dals/lentils and white butter.
Add water. Pressure cook for some 12-15 whistles.
Open and check if the lentils are cooked.
You should be able to mash the both the urad dal and rajma with spoon if they are cooked completely.
If they are not cooked thoroughly, then pressure cook for 2-3 whistles more.
Add water if required.
Now again open the cooker and let the dal makhani simmer in the cooker itself without the lid for 10-15 minutes or more till you get a smooth and creamy consistency and texture.
If you wish to add cream, you can add cream now and let the dal makhani simmer for 5 or 10 minutes more.
If you like then you can Garnish Dal Makhani with coriander-cilantro leaves (optional).
Serve dal makhani hot with hot rotis, naan, or rice.