Line 2 large baking sheets with parchment paper and preheat the oven to 400°F.
Cut each potato into 8 even-sized wedges: Cut in half lengthwise. Cut in half lengthwise again. Then cut the pieces in half lengthwise a final time.
Add the oil, garlic powder, garlic salt, ranch seasoning, and pepper in a large Ziploc bag. Add the potato wedges and toss until evenly coated.
Spread the wedges evenly, in a single layer on both baking sheets. Make sure that the skin side is facing down against the pan.
Sprinkle with half of the Parmesan cheese and, if needed, extra salt.
Bake for 28-30 minutes, turning the wedges halfway through. Bake until golden, crisp, and cooked through when tested with a fork.
While wedges are baking, make fry sauce by pouring all ingredients into a bowl and whisk until combined.
Sprinkle with parsley and remaining Parmesan Cheese and serve warm.