Preheat your oven to 400 degrees.
Cut your sweet potato into fries by cutting the ends off first then slicing lengthwise into thin slices then chopping each slice into fries. Line a sheet with parchment.
Whisk oil, egg and spices and sugar if using till slightly foamy and pour over the fries. Toss till evenly coated then arrange in a single layer. Bake approximately 40 minutes or till the desired level of doneness is reached.
While the fries are baking mix up the yogurt dip. When the fries are done, serve immediately with dip.