After soaking the dal, put in a heavy pot covering with water, and cook on a low heat for several hours until soft. Add the ginger, turmeric and chilli to the pot.
Temper the spices: put the ghee and butter into another pot and heat on a medium heat. Add the onion, fry till soft.
Add the garlic, ginger, spices, stir and fry for 5 or so minutes.
Add the tomato passata, stir and fry for 5 to 10 minutes.
Mash 1/3 rd of the lentils and add both the whole lentils and the mashed ones to the pot. Add the vegetable stock. Cook on a low heat for at least an hour.
Check seasoning regularly and add salt if necessary.
Add the liquid smoke and the cream.
When serving, add a knob of butter. Serve with Indian flatbreads or rice, and yoghurt.