01 - Preheat your oven to 350°F (180°C). Line a baking tray with parchment paper.
02 - Place the sourdough loaf on a cutting board. Using a serrated knife, make deep diagonal cuts across the bread, approximately 2cm apart, being careful not to cut all the way through to the bottom. Rotate the loaf and repeat the scoring process in the opposite direction, creating a crosshatch pattern.
03 - In a small mixing bowl, combine the softened butter, minced garlic, chopped parsley, thyme, salt, and black pepper. Mix thoroughly until a cohesive garlic herb butter is formed.
04 - Gently open the scored sections of the bread. Use a butter knife or spoon to evenly spread the prepared garlic herb butter into each cut, ensuring good coverage throughout the loaf.
05 - Evenly stuff the shredded mozzarella, cheddar, and grated Parmesan cheeses into the cuts of the loaf. Ensure the cheese is tucked throughout the bread.
06 - Place the cheese-stuffed loaf onto the prepared baking tray. Loosely wrap the loaf with aluminum foil to help prevent the exterior from over-browning during the initial baking stage.
07 - Bake for 15 minutes. Remove the foil and continue to bake for an additional 8-10 minutes, or until the cheese is fully melted and the top of the bread is golden brown and bubbly.
08 - Remove from the oven and serve warm. Encourage diners to pull apart pieces of the bread to enjoy the cheesy, garlicky goodness.