Heat your pizza oven to 400°F (200°C).
Wash and scrub your potatoes thoroughly.
Slice the potatoes thinly. Sweet potato slices should be about 1/8 inch apart, stopping just before you reach the bottom.
In a small bowl, combine olive oil, melted butter, minced garlic, sea salt, black pepper, thyme, and rosemary.
Brush the mixture generously over each sweet potato, making sure to get some of the mixture in between the slices.
Place the potatoes on an oiled cast iron skillet.
Put the skillet or stone in the preheated pizza oven.
Cook for about 25-30 minutes, or until the potatoes are crispy on the outside and tender on the inside. Rotate the skillet occasionally to ensure the potatoes cook evenly.
About 5 minutes before the potatoes are done, sprinkle the crumbled goat cheese or feta over the top (if using).
Continue cooking until the cheese is slightly melted and golden brown.
Remove from the oven and let them cool for a few minutes.
Garnish and serve with freshly chopped parsley before serving.