Heat the oil in a large pan over a medium heat. Add the onion and cook gently for 5 minutes. Add the garlic, ginger and red chilli and cook for a few minutes.

Grind the cumin, coriander and mustard seeds lightly in a pestle and mortar, then add to the pan, along with the turmeric and garam masala and cook for 1 minute.

Add the lentils, tomatoes with their juice, coconut milk and broth/stock, then stir to combine. Season with salt and pepper and cook on a medium/low heat for 15-20 minutes until reduced and thick. If you have time, you can leave it a little longer on a very low heat for even more flavor (just stir often and check it doesn't scorch on the bottom of the pan).Taste and add more chilli if desired.

Stir in the lemon juice and spinach until it wilts.

Serve warm with rice, naan bread or poppadoms.

Heat the oil in a frying pan over a medium heat. Add the onion and cook gently for 5 minutes. Add the garlic, ginger and red chilli and cook for a few minutes.

Grind the cumin, coriander and mustard seeds lightly in a pestle and mortar, then add to the frying pan, along with the turmeric and garam masala and cook for 1 minute.

Add the onion mixture to the bowl of the slow cooker, along with the lentils, tomatoes, coconut milk and broth/stock. Place lid on slow cooker and cook on high for 4-5 hours or low for 8-10 hours.

Taste and cook longer if necessary for the lentils to be lovely and soft. Season with salt and pepper and stir in the lemon juice and spinach.