Heat vegetable oil in a large pot or deep skillet over medium heat. Add the finely chopped onion and sauté for about 5 minutes, stirring occasionally, until soft and translucent.

Add minced garlic and grated fresh ginger. Cook for about 1 minute, stirring constantly, until very fragrant. Add curry powder, ground turmeric, and ground cumin. Stir constantly for about 30 seconds to toast the spices and release their essential oils.

Add cubed sweet potatoes and drained chickpeas to the pot. Stir everything together thoroughly, ensuring the vegetables are completely coated in the spice mixture. Cook for 1 to 2 minutes, stirring occasionally.

Pour in the full-fat coconut milk and add about 1/2 cup of water, just enough so the vegetables are barely covered. Bring to a boil over medium-high heat, then reduce heat to low to maintain a gentle simmer.

Cover the pot and simmer for 15 to 20 minutes, stirring occasionally, until the sweet potatoes are fork-tender and the sauce has thickened. The sweet potatoes should easily pierce with a fork but still hold their shape.

If using spinach or kale, stir it into the curry during the last 2 minutes of cooking until wilted. Taste and season with salt and black pepper as needed.

Remove from heat and let rest for 5 minutes. Serve hot over basmati rice, quinoa, or with warm naan bread. Garnish with fresh cilantro leaves and a squeeze of fresh lime juice.