1In a large saucepan, heat the oil over a medium-high heat.
2Reduce heat to medium, add the onions and cook for 10 minutes, stirring so they don’t burn.
3Add the garlic, ginger and chillies and cook for a further 5 minutes.
4Now add all the cumin, turmeric, ground coriander and peanut butter and stir until mixed in.
5Add the tomatoes and cook for 2 minutes, then add the mushrooms, mix in, and cook for a further 2 minutes.
6Add the potatoes and cook for 2 minutes.
7Add the coconut milk, bring to a boil, then reduce to a simmer. Simmer for approximately 20 minutes, or until the potatoes are cooked through. If using sweet potatoes instead, they will take longer.
8Add the spinach leaves and stir them in so they wilt.
9Stir in the garam masala, salt and pepper. Add a good squeeze of lemon, too.
10Ladle into bowls and garnish with fresh coriander. Serve alongside rice, poppadoms and/or naan bread.