Preheat oven to 450°F. Wash and dry sweet potatoes. Chop the ends off the potatoes and slice into ½ inch planks, lengthwise. Slice again lengthwise for ½ inch thick sticks. Toss with olive oil, salt and cumin in a large mixing bowl and lay out on a baking sheet with 1 inch of space between pieces. Bake for 15 minutes, remove from oven and flip fries with tongs and bake again for 6 minutes or until dark and crisp on both sides. Mix all ingredients for dipping sauce together in a medium mixing bowl. Refrigerate for at least 30 minutes before serving with fries.