Blitz the onion with the garlic, ginger and green chilli.
If using frozen spinach, microwave for 3 mins in a sieve over a bowl. Then squeeze out most of the water into the bowl. If using fresh spinach, place in a colander, pour over boiling water, drain and cool, then put in a tea towel and squeeze out most of the water into a bowl. Roughly chop.
Melt the ghee over a medium heat, whisk in with the turmeric and chilli powder, then add the cubed paneer. Cook for around 8 mins, tossing the pan so it becomes golden all over. Remove and set aside on a plate, leaving spices behind in the pan.
Tip the onion mix into the pan, add a pinch of salt and turn the heat down. Fry until caramel coloured, around 10 mins, adding a splash of spinach water if it looks a little dry. Add the garam masala, stir to coat the onion mix, fry for 2 mins.
Add the spinach and cook for a further 2-3 mins, adding 100ml of spinach water to release all the flavours from the bottom of the pan. Add the paneer and cook for 2-3 mins to heat through. Spoon into bowls to serve.