Peel and cut sweet potatoes into ⅓ to ½-inch thick matchsticks.
Place the matchsticks into a bowl and cover with cold water. Soak for at least 30 minutes.
Meanwhile, preheat the oven to 425 degree Fahrenheit. Line a sheet pan with parchment paper and set aside.
Mix up cornstarch, garlic powder, black pepper, and smoked paprika.
Drain and rinse sweet potatoes to remove excess starch. Thoroughly pat sweet potatoes dry then toss with avocado oil and cornstarch mix until evenly coated.
Spread sweet potatoes out on prepared sheet pan, leaving at least half an inch between each fry. If necessary, bake in batches or on separate pans to provide enough space.
Place pan on top oven rack and bake for 10-12 minutes then flip the fries and return to oven for 8-10 more minutes.
While the fries bake, prepare the garlic herb butter: Stir together the melted butter, parsley, garlic, and sea salt. Set aside.
Remove pan from oven and allow fries to rest for about 5 minutes then toss in the garlic herb butter and again in grated parmesan. Serve warm.