Bring a large pot of water to boil. Scrub the potatoes clean with a sponge. Place the whole potatoes in the boiling water and cook them until they are soft enough to pierce with a fork but aren't falling apart.
Cut the potatoes into 1-inch cubes. Next, slice the fish into similar-sized pieces. Lay the potatoes and cod on a baking sheet in one single layer. Season both generously with garlic parsley salt.
Bake it at 425°F for 15 minutes. Then, turn the oven onto a high broil for a few minutes, just until the fish and potatoes develop a nice crust. Serve immediately and enjoy!