If using the cashews, soak them in hot water for 15 minutes then grind in a blender or blitz in a food processor.
Slice and chop the onion and mushrooms.

Heat the oil in a pan and add the mustard seeds. When they start to crackle and pop, add cumin seeds and fenugreek (if using).Cook for a minute or so on a low heat to prevent burning.

Add the onions and stir the seeds through. Cook gently until onions have softened.
Add the ginger and garlic and cook until they no longer smell raw.
Add the tinned tomatoes and then the turmeric, chilli, garam masala and coriander.
Now add the lentils and stir through. Add 1/2 cup water and leave to simmer for about 20 minutes. If the mixture becomes too dry, add more water.
Now add the mushrooms and stir through.
Add the coconut and cashew paste and the curry leaves.
Taste and add salt to your taste.
Cook for a further 5-7 minutes. Too long and the mushrooms will cook down to nothing.
Serve with rice, garnished with fresh chopped coriander