1. Preheat Your Oven and Prepare the Bread: Start by preheating your oven to 375 F (190 C). While the oven heats, take your sourdough loaf and slice it horizontally almost all the way through, creating thick slices that are still connected at the bottom crust. This allows the garlic butter to seep into every crevice while keeping the loaf intact for serving. Alternatively, you can slice the loaf completely into individual pieces if you prefer.

2. Create the Garlic Butter Mixture: In a small bowl, combine the softened unsalted butter, minced garlic, chopped fresh parsley (if using), salt, and black pepper. Use a fork or a small spatula to mix everything together until it’s well combined and forms a spreadable paste. The butter should be soft enough to mix easily but not melted.

3. Spread the Flavor: Generously spread the garlic butter mixture between each slice of sourdough bread. Don’t be shy – make sure to get a good amount on both sides of each slice. If your loaf is still connected at the bottom, gently pry open each slice to ensure even coverage. You can also spread some butter on the top crust for extra flavor and a beautiful golden finish.

4. Add Optional Cheese: If you’re using Parmesan cheese, sprinkle it generously over the buttered surfaces of the bread, both between the slices and on top. This will add a delicious cheesy crust and a savory depth.

5. Wrap and Bake: Carefully wrap the entire loaf in aluminum foil. This step is crucial for allowing the bread to steam slightly and absorb all the delicious garlic butter flavor without burning the crust. Place the foil-wrapped loaf directly on the oven rack or on a baking sheet.

6. Initial Bake: Bake the wrapped sourdough garlic bread for 15 minutes. This initial bake allows the butter to melt, the garlic to infuse, and the bread to warm through.

7. Final Browning (Optional): After 15 minutes, carefully remove the foil from the top of the bread, exposing the crust. Return the unwrapped loaf to the oven for another 5-10 minutes, or until the edges are golden brown and slightly crispy. Keep a close eye on it to prevent burning.

8. Serve Warm: Once baked to perfection, remove the garlic bread from the oven. Let it cool for just a minute or two before slicing completely (if not already sliced) and serving warm.