I got this recipe from Well and Good. It was tasty but watch out for your blood sugar.
1 large sweet potato, peeled and cut into chunks (about 2 cups)
1/3 cup black rice
1 cup water
1 Tbsp cocoa powder
Pinch of ground red pepper
Pinch of ground black pepper
1/2 tsp sea salt
1 can (15 oz.) coconut milk
1. Place a steamer basket in a large pot with 2 inches of water. Bring to a boil over high heat. Steam the sweet potato in the basket for 12 minutes, or until the potato is very soft and easily pierced with a knife. If you do not have a steamer basket, fill the pot with 1 inch of water and bring to a boil over high heat. Add the sweet potato. Reduce the heat to low, cover, and cook for about 10 minutes. Allow the potato to cool to room temperature. Reserve the water.
2. Meanwhile, in a medium pot over high heat, combine the rice and water, cover, and bring to a simmer. Reduce the heat to medium-low and cook for 40 minutes, or until the rice is tender.
3. In a blender, combine the potatoes, the reserved steaming water, cocoa powder, red pepper, black pepper, salt, and coconut milk. Puree to a smoothie consistency.
4. Stir in the black rice. Enjoy warm or chilled.