The first time I had this dish was at the Hellmand Afghani Restaurant in San Francisco. I fell in love immediately and went on a quest to recreate the flavors of this dish. It was called Pumpkin with Meat Sauce. I have switched to sweet potatoes because I like them better and they are more readily available year round.
Peel and dice the sweet potatoes to bite sizes. At this point you can either bake them in the oven for the entire time OR you may parboil them until just barely tender, drain and then proceed to step two.
Pour some of the vegetable oil (DO NOT USE OLIVE OIL) onto a jelly roll pan and use it to grease the pan well and then spread the drained sweet potato chunks out on the pan. Pour remaining oil over the potates and sprinkle the white sugar over it. Bake in a 400 degree oven for 15-20 minutes stirring once if you parboiled them. If the potatoes are raw when you start this process, bake until tender stirring every ten minutes (probably 40-45 minutes).
Finely chop the onion while heating a couple tablespoons of vegetable oil in a skillet until it ripples. Add the onions, stir frequently and sautee until golden brown 10-15 minutes.
Add the ground beef and saute until the meat is no longer pink or about 5 minutes.
Dice up the tomato and mince the garlic. Add to meat and onions along with the coriander, salt, pepper and tumeric. Cook for 5 minutes.
Add 2-3 tablespoons of tomato paste and all the water bringing the mixture to a boil over high heat before covering, turning the heat down and simmering for about 15 minutes.
Plate with the sweet potatoes as the base and the meat sauce ladled over it.