Heat oil in a skillet over medium heat. Put onion, garlic, and ginger, in the pan and cook until softened, but not brown.
Add coconut milk, tomatoes, chickpeas, and sweet potatoes. Stir and bring to a boil, then reduce heat to medium-low.
Simmer until sweet potatoes are tender and sauce is thickened, about 15 minutes
Stir in garam masala, chilli flakes, cumin, and salt. Simmer for 15 minutes, stirring occasionally.
Just before serving, stir in baby spinach until just wilted.
Serve hot, with naan bread or basmati rice.
Coconut milk is a key flavour in this type of curry. It also gives the curry a rich, creamy texture. However, a drawback of using coconut milk is that it is high in fat and calories, so this recipe uses light coconut milk, which is 60% lower in fat and calories.