1. Peel the purple potato and peel the sweet potato, and cut into pieces separately.
2. Steam on high heat for 15 minutes
3. Crush the sweet potatoes and purple potatoes with a spoon.
4. Blanch cranberries, remove and chop.
5. Prepare the mold, put the mashed sweet potato, cranberry, and mashed purple potato into the mold in turn to compact.
6. Unmold, pour yogurt and fruit.
