These burgers are hearty and slightly sweet with mild Indian spices. For quick and easy assembly, prepare the rice and sweet potato ahead of time. Sweet potatoes cook easily in a microwave in about six minutes. The burgers are delicious served in a bun or on their own topped with mango chutney, pickled red onions, and chives. They also make a fun appetizer, slider-sized, atop a toasted mini pita or bun. As an added bonus, these burgers freeze very well. Make a batch or two, eat some now, and freeze the rest for later.