Preheat the oven to 400°F (200°C). With a sharp knife, slice the bread lengthwise through the center to create two long halves. Lay out two overlapping pieces of foil, each approximately 24 inches long, on a rimmed baking sheet. Position both bread halves cut side up on the prepared tray.

In a medium-sized mixing bowl, combine the softened butter with olive oil, garlic, salt, and pepper. Stir the mixture thoroughly to create a smooth, seasoned spread. Evenly distribute this mixture over the exposed surface of both bread halves, ensuring the edges are well coated to prevent burning.

Wrap the foil up and over the bread, folding and crimping the edges securely. Tuck the ends of the foil under to seal. Place in the preheated oven and bake for 10 minutes.

Carefully remove the tray from the oven and peel back the foil, rolling it inward to expose the top of the bread. Sprinkle both halves generously with mozzarella and parmesan, distributing the cheeses evenly.

Return the bread to the oven and bake uncovered for an additional 5 to 6 minutes, or until the cheese is melted and bubbly. For a more golden and crisp finish, activate the broiler during the final 1 to 2 minutes of baking, monitoring closely to avoid over-browning.

Once baked, remove from the oven and sprinkle evenly with chopped parsley. Slice the bread into portions and serve promptly while warm.