Prepare your cookware as needed. Cooking times and results may vary depending on your equipment and ingredients.
Preheat the oven to 400°F (204°C) and line a baking sheet if desired.
Slice the bread lengthwise and place the halves cut-side up on the baking sheet.
In a bowl, mix softened butter, garlic, parsley, salt, and Parmesan (if using) until evenly combined.
Spread the garlic butter evenly over the bread, pressing gently so it adheres.
Bake 16–18 minutes, until the edges are lightly golden and the surface is crisp and the bread feels warm and crisp on the surface. Cooking time may vary by oven and loaf thickness.
Remove from the oven and let rest briefly before slicing. Serve warm.