In the pan used to fry the tofu, over high heat, add the mustard seeds, asafetida, cinnamon stick, cloves and green cardamom pods. After the mustard sputters and pops, add the onions along with a pinch of salt.
Sauté the onions 3-5 minutes over medium heat until just beginning to brown. Stir in and sauté the garlic until you can smell the aroma, about 30 seconds.
Add the tomatoes, ground coriander, ground cumin, cayenne and turmeric to the pan. Mix everything and cook until the tomatoes are very soft and pulpy.
Stir in the ginger garlic paste and sauté another 30 seconds.
Add the pureed greens to the onions and tomatoes with 2 cups water.
Add sugar and garam masala to the greens. Mix well and let the greens simmer, without covering the pot, for 10 minutes or until the greens don't taste raw anymore. Stir frequently and add some water if the greens start sticking to the bottom of the pan.
Stir in the browned tofu cubes and the cashew cream. Mix well, return to a boil, then lower heat and simmer for a couple of minutes. Check for salt and turn off heat. Serve the methi chaman hot.