Heat the oil in a large saucepan and fry the sliced onion, garlic and cumin seeds.
After a couple of minutes add the ginger, chilli, cumin powder and tumeric.
When all the onion is coated with the spices add the can of peeled plum tomatoes – bash them with the wooden spoon to break up if they’re not ready chopped.
Add the mushrooms and leftover lamb and stir. Allow the curry to simmer for five minutes.
If using fresh spinach, pop the leaves on top of the curry and put the lid on so the leaves can steam inside. (If using frozen, microwave it for 1-2 minutes at this point, then add to the curry)
Simmer for another five minutes. Add the garam masala and ground coriander and serve.
Notes
This lamb curry with mushrooms can be served with rice or flat breads.The instructions here are to make this quickly as a midweek dish, you can leave it simmering on a low heat for longer if you wish.