Scrub and pierce sweet potatoes. Bake at 400 degrees for 1 hour or until tender. In a small saucepan, saute onion in butter until tender. Add cranberries, syrup, water, cranberry juice and 1/8 teaspoon salt. Bring to a boil. Reduce heat; cover and simmer for 10 - 15 minutes or until berries pop, stirring occasionally. Stir in walnuts and mustard; heat through.
Cut potatoes in half lengthwise; sprinkle with pepper and remaining salt. Top each with 2 tablespoons cranberry mixture; sprinkle with chives.
Yield: 8 servings