Dry fry the sliced onion with a pinch of salt in a large heavy-based saucepan over a medium heat until softened and starting to colour. Add a splash of water if the onions start to catch.
Add the mustard seeds and cook for a further two minutes.
Add the garlic, ginger, tomato, tomato paste, chilli, garam masala and chickpeas and cook for a further 2 minutes, stirring.
Add 3 tbsp water and cook for another two minutes. The consistency should be quite thick.
Stir in the spinach, then cover and leave for another 4 minutes to wilt.
Uncover, add a squeeze of lemon juice and stir everything together.
Take off the heat then stir through the yogurt.
Serve with naan bread, plain rice (microwave rice can be used here) and top with more yogurt and cilantro.
Note: If freezing add the yoghurt after reheating.