Preheat the Oven: Heat your oven to 375°F (190°C).
Prepare Garlic Butter: In a mixing bowl, combine butter, garlic, parsley, salt, pepper, and Italian seasoning. Mix until smooth and creamy.
Prepare the Bread: Cut the sourdough loaf in half horizontally (or into thick slices if preferred). Place on a baking tray lined with parchment paper.
Spread the Mixture: Generously spread the garlic butter mixture over each half of the bread.
Add the Cheese: Sprinkle mozzarella, Parmesan, and cheddar evenly over the top. Add chili flakes if you like a mild kick.
Bake: Place in the oven for 12–15 minutes until the cheese melts and the bread turns golden around the edges.
Broil (Optional): Turn the oven to broil for 1–2 minutes for that bubbly, crisp cheesy top.
Slice and Serve: Slice into thick pieces and serve warm. Perfect with pasta, soups, or as a snack!