Wipe the mushrooms with kitchen paper and slice in 1/4 inch slices.
Heat 2 tbsp oil in a large pan over medium-high heat. Add the mushrooms in a single layer (in two batches if your pan is small) and leave them for 3 to 4 minutes until golden underneath. Stir and cook for another 3 to 4 minutes. Season with ½ tsp salt once browned, then tip them onto a plate.
500 g chestnut mushrooms, 2 tbsp olive oil, 0.5 tsp salt
Rinse the lentils and set aside. Peel and chop the onion. Peel and finely mince or grate the garlic and ginger. Chop the chili finely, removing the seeds if you prefer it milder.
Lower the heat to medium, add the remaining 2 tbsp oil and the onion. Cook for 5 minutes until soft and lightly golden.
2 tbsp olive oil, 1 large onion
Add the nigella seeds and curry leaves and let them sizzle for about a minute. Stir in the garlic, ginger and chili for 1 minute, then the cumin, garam masala, turmeric and black pepper for 30 seconds.
2 tsp nigella seeds, 4 garlic cloves, 1 tbsp fresh ginger, ½ fresh green chili, 1 tsp ground cumin, 2 tsp garam masala, ½ tsp ground turmeric, ½ tsp black pepper, 5 dried curry leaves
Add the rinsed red lentils and the stock, partly cover and simmer for about 20 minutes, stirring often. Keep a splash of hot water ready in case it starts to catch. They’re ready when they’re soft and almost mushy, which is what makes the sauce creamy.
100 g red lentils, 500 ml vegetable stock
Make a little space in the pan, add a drizzle of oil and stir in the tomato paste. Cook for 1 to 2 minutes until it darkens slightly and starts to stick to the pan.
2 tbsp tomato paste
Stir in the chopped tomatoes and simmer for 5 minutes, stirring so the base doesn't catch. Taste and adjust the seasoning if needed.
200 g chopped tomatoes, 0.5 tsp salt
Add the spinach a handful at a time, pressing it into the curry until wilted, about 2 minutes. Stir the mushrooms back in to warm through, then take off the heat.
200 g spinach
Spoon over rice or serve with naan, scatter with coriander or parsley, and top with pickled red onions and a spoonful of yogurt or raita.
fresh coriander (cilantro) or parsley, quick pickled red onions