Heat the oil in a deep frying pan or saucepan. Add the onion, courgette and mushrooms, and cook over a medium heat for a few minutes until fairly soft. Add the diced halloumi and garlic, and cook for a further 5 minutes until any excess water has cooked off, and the cheese and vegetables are just starting to brown slightly.
Add the lentils, tinned tomatoes and vegetable stock, along with all the spices. Mix well, then cover the pan with a lid and bring to a simmer. Leave to cook for around 30 minutes, stirring occasionally, until the lentils are soft and the curry has reached your desired consistency. For a saucier curry, or if the lentils need to cook a little longer, you can add a dash more water or stock. For a drier curry, remove the lid and cook for a few minutes to thicken.
Serve warm with your choice of sides.
