(modified slightly by Gene from the Recipe Source website)
Heat the oil in a large frying pan over medium-high heat for 3 minutes. Add the onion and cook, stirring, for 3 minutes. Add the ginger, garlic, chilies, and cumin seeds, and cook for 2 more minutes.
Add the turmeric, mushrooms, and salt. Cook, turning them, until all the moisture evaporates and the mushrooms begin to fry (about 15 minutes). Lower the heat, sprinkle on the lemon juice, mix well, and continue cooking until the mushrooms absorb the lemon juice and look fried (about 5 minutes). Turn off the heat and serve warm, at room temperature, or cold, sprinkled with chopped fresh coriander. Serving over basmati rice is also nice.