Preheat oven to 400 F. Preheat clean cast iron pans in oven as well.
Scrub potatoes until clean. Cut potatoes into 2.5 cm/0.5 inch cubes and slice sweet potatoes into wedges about 2.5 cm/ 0.5 inches at the widest part. Soak in cold water for a few minutes. Note: I have read the longer you soak the fries the crispier they will be. I however usually don't plan that far ahead. Soak up to 24 hours.
Drain excess water on a clean tea towel.
Parmesan Sweet Potato Fries
Toss potatoes in half butter and half olive oil with a pinch or two of sea salt.
Spread fries on a preheated cast iron pan. Bake at 400F for 15 minutes.
Finely grate some parmesan cheese.
Turn fries and sprinkle parmesan cheese on top. Bake another 10 minutes until golden and cheese is crispy.
Garlic Herbed Potato Fries
Toss potatoes in half melted butter and half olive oil, a few cloves of garlic, 1 Tablespoon dried oregano, a pinch or two of salt and some pepper. These are all to taste.
Bake at 400 F for 10 minutes, toss, bake 10 minutes, toss, bake another 5 minutes until golden.