Preheat the oven to 375°. Prick the yam with a fork and bake for about 45 minutes, or until very soft. Alternatively, microwave the yam. Let cool, then peel and mash the yam until smooth; set aside 3/4 cup. Leave the oven on.
Coat a large baking sheet with cooking spray. In a bowl, combine the 3/4 cup yam with the sugar, oil, egg, orange zest and vanilla. In a medium bowl, whisk together the flour, baking powder, cinnamon, ginger, cardamom and salt. Stir the dry ingredients into the yam mixture just until combined. Divide the dough in half.
Working on a lightly floured surface, pat the dough into two 6-inch rounds. Cut each round into 6 wedges and brush the tops with the maple syrup. Arrange the wedges on the prepared baking sheet and bake for about 20 minutes, or until golden and cooked through. Serve warm.
One Scone Calories 123 kcal, Total Fat 2.9 gm, Saturated Fat .3 gm