Preheat your oven to 400° F (or 200° C). Line a baking sheet with parchment paper.
Prep your sweet potatoes by cutting them into 1/4 inch thick rounds. Use either a sharp knife or a mandolin. Arrange your potatoes on a baking sheet, slightly overlapping them.
In a small bowl, mix together parmesan & gruyere cheese, herbs de provence, salt, pepper, rosemary and garlic.
Brush the potatoes with melted butter and sprinkle on top the cheese mixture.
Place in oven for 25 minutes. Once potatoes are cooked and golden brown, remove from oven and sprinkle with fresh parsley (if desired)