Heat oil and butter in a wide pan or large skillet(1 use a 12 inch pan).
Sprinkle the cumin seeds over and let crackle.
Stir in the chopped onions and sauté over medium heat for 3-5 minutes, or until translucent.
Next, add chopped green chilies, garlic paste, and the powdered spices—red chili powder, coriander powder, and turmeric powder. Cook for 1-2 minutes, stirring, until the raw aroma of garlic disappears and the spices are fragrant.
Add the chopped bell peppers and mushrooms to the pan. Sauté for 3-4 minutes, allowing the mushrooms to soften slightly.
Pour in the tomato sauce or puree and mix well with the mushroom mixture. Cook for another 2-4 minutes, or until the mushrooms are fully softened.
Season with salt, garam masala powder, and amchur (or a squeeze of lemon juice). Add chopped cilantro leaves. Stir well and turn off the heat.
Let the mushroom masala cool slightly in the pan, then fold, softened cream cheese, and mozzarella cheese.
Mix thoroughly to combine. Your cheesy masala mushroom filling is ready to use!