Heat oil in a skillet on medium heat.
Thaw the puff pastry squares or sheets in the refrigerator.
Heat oil in a heavy-bottomed skillet over medium heat. Add cumin seeds and allow them to crackle.
Next, add sliced onions, and saute on medium to medium-low heat until golden brown.
Add coarsely crushed ginger-garlic, and stir-fry until fragrant.
Add diced tomatoes along with salt, mix, cover, and cook on medium-low heat for 1 to 2 minutes.
Remove the lid, and saute until tomatoes turn mushy.
Next, add Kashmiri chili, coriander, black pepper, turmeric, and garam masala powders, mix well and saute for another 30 seconds.
Add tomato ketchup and mix well.
Add water and mix well.
When the mixture starts to bubble, add cubed paneer, mix gently, and cook for another 2 minutes on medium-low heat.
Switch off the heat and add lemon juice, and finely chopped coriander leaves. Mix gently and set aside to cool down completely. This makes about 2¼ cups of paneer filling.