Thaw the frozen puff pastry sheets as per package instructions. Alongside, once you take out the pastry sheets from freezer for thawing, immediately start working on the filling.
For the filling, heat oil in a non-stick pan or skillet and add cumin seeds to it. Once it splutters, add onions to it. Saute onions till they are light golden (don't brown them). Add chopped tomatoes and saute them again for a minute. Now, add the spices (salt, coriander powder, turmeric powder, garam masala, kasuri methi, black pepper and red chili pepper) and tomato ketchup and saute for another minute. Finally, add the Paneer dices, saute for a minute again and switch off the flame. Keep aside the filling for later use.
Take the thawed pasty sheet, unfold it carefully, spread some flour on your kitchen surface (where you want to prepare the puffs) and lightly dust both sides of the sheet. Cut it into 9 (3*3) equal squares as shown in the picture. Preheat the oven to 400 degree F. Prepare egg wash by beating 1 egg in a bowl and keep it aside.
For making one puff, take one square and roll it from all sides using a rolling pin (For measurement idea, I rolled the square from ~3 inches to a 4-5 inch square for final use). Apply egg wash using a pastry brush to the 4 sides of the sheet (on the side facing up). Add ~1 Tbsp of filling in the center of the sheet. Fold the pastry sheet into a triangle carefully. Then, using a fork, create a design on the folded sides very carefully. Put the triangular pastry on the baking tray lined with parchment paper.
Repeat the above step for all the pastry squares.
Finally, apply egg wash on top part of all the prepared pastry triangles.
Bake the prepared pastry triangles in the preheated oven for around 18-20 minutes. Once done, remove the baking tray from the oven.
Serve the hot and flaky Paneer Puffs with a sauce or dip of your choice.