Preheat the oven to 425°F. Coat the baking sheet with 1 tablespoon of oil and set aside. Place the potatoes in a pot and cover with water. Bring to a boil and cook until fork-tender, about 15 minutes. Drain the potatoes.
Use tongs to transfer the very hot potatoes to the oiled baking sheet. Use the back of a heavy measuring cup to smash each potato. (They should be about 1/4-inch thick.) Drizzle the potatoes generously with the remaining oil and sprinkle with salt, garlic, and pepper.
Roast for 30-35 minutes, until browned and crispy on the edges. Remove from the oven, and top with cheddar cheese and bacon. Roast an additional 5 minutes to melt the cheese.
Remove from the oven and top with Parmesan, green onion, and parsley. Serve warm.