All sorts of leafy greens work in this dish—kale, chard, spinach, whatever you have. Just keep in mind whether the leaves are delicate or more substantial and cook for the appropriate amount of time. You can substitute turnips or rutabaga for the potatoes if you like. Serve with raita (a cooling yogurt dish) and Indian flat bread such as naan (available frozen at Trader Joe’s). You’ll find all the spices at most grocery stores and any Indian market.