Pressure-cook urad dal and rajma in about 4-5 cups of water with a little salt till 8 whistles are given out. Drain and reserve the cooking liquid.
Chop onions and garlic. Cut the ginger into thin strips. Heat ghee and butter in a deep non-stick pan.
Add cumin seeds and sauté for a few seconds. Add onions, garlic and ginger. Sauté for 2 minutes or till lightly browned. Puree tomatoes.
Add red chilli powder and tomato puree to the onions. Mix well and cook till fat separates. Add cooked dals and 1½ cups of cooking liquid. Mix well.
Add garam masala powder. Mix well and cook on low heat for 15-20 minutes, stirring frequently. Add cream and stir to mix. Serve hot garnished with a swirl of cream and a coriander sprig.