Heat oven to 375°F. Pierce sweet potato several times with tines of a fork. Place sweet potato inside a loose nest of foil. Bake until tender when pierced with the tip of a paring knife, 40 to 50 minutes. Remove them from oven and let cool enough to handle.Open sweet potato across the top, pushing the flesh slightly so it rises out of the skin. Spoon on yogurt and syrup. Sprinkle with nuts, and serve.Make-Ahead Tip: One or more sweet potatoes can be cooked ahead of time and kept refrigerated for about 5 days. To warm, place it in a microwave on medium-high for one minute or in a toaster oven for 5 minutes.