Wipe the mushrooms with a wet paper towel to get the dirt off. Mushrooms have a lot of water in them and washing them in water makes them even more moist and kind of mushy so wiping them clean works better. Slice the mushrooms.
Set a heavy bottomed non stick or cast iron skillet on medium high heat. Add half a tablespoon of oil to the skillet and add the mushrooms. Let the mushrooms sweat and loose their moisture till they turn a nice deep brown in color and look a bit dried.
While the mushrooms are cooking, finely chop the onion, tomato and green chili (if using) and mince garlic.
Once the mushrooms are done, take them out in a bowl and add the remaining oil to the pan. Break apart the pod of green cardamom. Once the oil is shiny and hot, add asafoetida, cumin seeds and green cardamom. Wait for the cumin seeds to splutter and then add minced garlic, turn the heat to low so that the garlic does not burn.
Wait for 30 seconds before adding green chili (if using) and onions. Turn the heat back up to medium high and add a pinch of salt to the onions. Adding salt to onions helps to pull out the moisture and they cook faster.
Cook the onions for 2-3 minutes, then add turmeric, red chili, toasted cumin, and coriander powders and mix.
Add the chopped tomatoes and cook for another 2-3 minutes. Then add about a ¼-cup water along with green peas and cooked mushrooms. Cover and let cook for 5 minutes.
In a small bowl, mix the heavy cream with kasuri methi leaves (see notes). Uncover the pan, add the cream and kasuri methi mixture, followed by salt and garam masala. Give everything a big mix, cover and cook another 2-3 minutes for the flavors to mingle.
Check and adjust seasonings, sprinkle chopped cilantro and serve hot with rice or roti. Enjoy!