Heat oil in a skillet over medium-high heat, add sliced onion to the hot oil, sprinkle salt, reduce the heat to medium, cook for few minutes, then add ginger garlic paste. Continue cooking until onions are softened.
Add all ground spices, give a good stir and continue cooking until onions are cooked and develop a good amber colour. It will take 10-12 minutes.
Add garam masala powder, coriander leaves, mix well and remove from heat.
For assembling the puffs:
Preheat your oven on 350° F or 180° C.
Line a couple of large baking sheets with parchment paper and set aside.
Whisk an egg with some water for the egg wash.
Arrange puff pastry sheets on a baking tray. Put a spoon full of onions mixture in centre of the puff pastry sheet. Then put half egg and seal the ends of puff pastry by bringing the 2 corners together in the centre. Repeat with the rest.
Brush the top off the puffs with the egg wash.
Bake in a preheated oven for 15 to 20 minutes at 180° C till golden brown or as per instructions given on puff pastry packet.
Serve them warm with your favourite dip and enjoy!