Start with sweet potatoes and onions - cube the sweet potatoes and dice the onions. Get the sweet potatoes cooking. I used a pressure cooker and you could also boil them.
Once the onions have softened, add 1 small chopped tomato, tumeric, garam masala, two or three cloves, half a cinnamon stick, salt, and the ground spices and fry up the mix for about 5 minutes. Frying the spices in the oil extracts the flavors, and changes them a bit. To get the flavors, you only need to fry for 2-3 minutes, but I let it go longer to cook the tomatoes more. The result is a nice masala paste.
Many different foods could be added to the paste to make a good curry - chicken, beef, shrimp, chickpeas, potatoes, cauliflower, eggplant or almost anything else. Add the cooked sweet potatoes, a spoonful of tamarind paste, the juice of half an orange, and a spoonful of brown sugar. I would not add anything other than the vegetables/meat for other curries (maybe the tamarind, and I would have used more tomato), but sweet potatoes have a sweetness I wanted to enhance. The orange juice is a holdover from many American sweet potato dishes that works with the tamarind here.
Mix it all up, and you're done!