Into a large pot place young tender spinach and add 3-4 tbsp of water. Cover with a lid and set over a low flame and cook for 3-5 minutes or until the spinach just starts to wilt down.
Remove the pot from the heat and run the spinach under cold water to stop the spinach from cooking further. Squeeze the spinach in batches to remove excess liquid and then roughly chop it. Place into a bowl and set aside.
Into a large pan melt unsalted butter over a medium flame. When the butter has warmed through, add the chopped onions and 1 tsp of salt. Sauté until the onions have softened. Then add ginger, garlic and green chilli and sauté for 60-90 seconds to cook out any rawness.
Next add chilli powder, turmeric powder, garam masala powder and stir for another 60 seconds to release the aromas of the spices. Tip the chopped tomatoes in and cook until the tomatoes have completely disintegrated into the onion masala.
Into the bowl of cooked spinach add the onion masala, chopped paneer pieces, egg yolk and season with a pinch of salt. Mix well and set aside.
On a lightly floured surface, roll out a sheet of all butter puff pastry into a 28 x 42 cm rectangle size. Then using a 14 cm diameter bowl cut out 6 puff pastry rounds from the dough.
Next add 1 generous heaped spoonful of the spinach and paneer mix to 1 side of the circular cut out. Wet the rim of the empty side with water and bring across to cover the filled half.
Press the rim of both ends together with your fingers to create a seal. If you want you can also press the edges with a fork to give the edges a pattern and seal it completely.
Brush the pasty lightly with a beaten egg and create a slit at the top to let steam escape. In a preheated the oven to 200°C/180°C fan/Gas Mark 6 bake the pasty’s for 25-30 minutes until golden brown. Remove from the oven and leave to rest for at least 10 minutes before serving.