FOR THE PASTE: Heat ghee over pan on medium heat. Sauté onions for 2 minutes, then add tomatoes and ginger-garlic paste. Cook for about 5 minutes.
Remove from heat and dump contents into blender. Blend into a smooth paste and set aside.
Heat olive oil in pan over medium heat. Add mushrooms and fry for about 3 minutes.
Add green chiles, chili powder, curry powder, garam masala, turmeric, and salt. Cook for about 20 seconds and immediately add the paste. You can add about 1/2 cup of water for consistency. Cook until mushrooms are tender.
Add chopped scallions. Cook for 2 minutes more and remove from heat.