Heat oil and butter in a pan and add cumin seeds.
When sizzling and aromatic add the minced onions and fry until golden colour.
Add the tomatoes, salt, turmeric, chilli powder and fresh chillies.
Stir together and leave to cook so the tomatoes break down and you are left with a thick paste.
Add the mushrooms and beans to the masala and stir. Cook for about five minutes
Pour in the coconut cream and cook gently for a few minutes so the flavours combine.
Reduce the heat and leave to cook for about 10 minutes before adding the peppers.
Taste the sauce and adjust seasoning if required.
Remove from heat and add garam masala and throw in the fresh coriander to serve.