Preheat oven to 425 degrees F.
Place cut potatoes in a large bowl and drizzle with oil + melted butter. Add the parmesan cheese, garlic, brown sugar, cumin, smoked paprika, ginger, cinnamon, saffron (if using), cayenne, salt and pepper. Gently toss with your hands or two spatulas to evenly coat. Spread the fries among two baking sheets in one even layer. Bake for 15-20 minutes, then flip and bake for 15-20 minutes more at 400 degrees F. You want the sweet potatoes to be crispy, but not burnt. If you want perfectly crisp fries I recommend spreading the sweet potatoes on a greased wire rack on top of a baking sheet and baking them as directed above. But this way is a bit of a pain.
While the fries are baking, make the dip. Add the feta, cream cheese and greek yogurt to the bowl of a food processor. Puree for 2-3 minutes or until smooth and creamy. Add 1-2 tablespoons harissa (I used 2) and puree until evenly mixed. Spoon the cheese into a small oven safe dish. Place the brie overtop the dip.
Place the dish on a small baking sheet and bake at 400 degrees F. for 15- 20 minutes or until the cheese is hot throughout.
Remove the fries from the oven and sprinkle with chopped fresh cilantro and flakey sea salt. Serve the fries warm with a dollop of cheese for dipping.