Cut up yams into cubes and boil app. 20 minutes. Drain and cool. Preheat broiler. In a small bowl, partially mash black beans and set aside. Chop green onions and garlic and combine with oil in skillet or pan. Cook over medium heat, stirring until softened, 2 to 3 minutes. Stir into beans. Chop parsley and set aside. Grate cheese or use pregrated.
Set up components on work surface. Lay down tortillas. First put 1/4 bean mixtures over half of each tortilla, followed by 1/4 of yams, cranberries, red pepper, and cheese.
Fold bare half of each tortilla over filling. Arrange on baking sheet or shallow baking pan and place under broiler for 3 minutes or til toasty on top. (Five minutes was too much!).
To serve, cut each tortilla into wedges and top each wedge with 1 teaspoon of sour cream, then sprinkle with chopped parsley. Serve immediately.
**For reduced fat version, use reduced fat cheese and sour cream or top with plain yoghurt. Any kind of sweet potato can be used, but we prefer the garnet yams. Dried cherries or currants would be good in place of cranberries. You might like to add more cheese for more of a "melt" effect. I thought the red bell peppers could be optional.