1. Heat 1 tbsp oil in a deep non-stick frying pan over a medium-high heat. Brown the lamb in batches (without overcrowding the pan) for 5-8 mins. Season and transfer to the slow-cooker.
2. Add the remaining oil to the pan and cook the onions and carrots for 10 mins over a medium heat until softened. Add the garlic, ginger, chopped green chilli, spices and coriander stalks. Stir well and cook for a further 1 min until fragrant. Transfer everything to the slow-cooker.
3. Add the chopped tomatoes and lamb stock to the slow-cooker and stir to combine. Cook on a low heat for 6 hrs.
4. Stir through the coconut milk and cook for a further 30 mins. Add the spinach to wilt through 5 mins before serving. Scatter with sliced chilli and coriander leaves, and serve with rice or naan, if you like. 

Tip: Short on ingredients? Use a ready-made curry paste to make this curry even easier. Replace the garlic, ginger, chopped chilli, dried spices and coriander stalks with 4 tbsp rogan josh curry paste: add in step 2 after the onions and carrots are softened, cook for 1 min, then transfer everything to the slow-cooker and continue with the recipe.