Place cut sweet potato matchsticks in a large bowl. Cover with cold water and let soak for 1 hour. (or up to 8 hours)
Preheat oven to 425F. Line two baking sheets with parchment paper. Set aside. Remove sweet potatoes from cold water and let drain well. Pat completely dry with paper towels and place in a large bowl. Toss with melted coconut oil until evenly coated.
In a small bowl, combine cornstarch with cayenne, paprika, and garlic powder. Toss into sweet potatoes until evenly coated.
Divide sweet potatoes between baking sheets, making sure to space out sweet potatoes into a single layer. Bake sweet potatoes at 425F 15 minutes, then flip fries over to opposite side. Return to oven and bake an additional 10-15 minutes until fries are crispy and tender. Let cool 10 minutes.
For serving, place sweet potato fries in individual serving bowls and drizzle chimichurri over top. Top with Parmesan if desired. Serve immediately and enjoy!