Step 1: Preheat your oven to 375°F (190°C). Line a baking sheet with parchment paper for easy cleanup.
Step 2: In a small bowl, combine the melted butter, minced garlic, chopped fresh parsley, salt, and black pepper. Stir until well combined.
Step 3: Take your loaf of bread and, using a sharp serrated knife, make deep crosshatch cuts across the top, going almost all the way through to the bottom crust but not quite. The cuts should be about 1 inch apart in both directions.
Step 4: Gently pull apart the bread slices in the cuts and generously spoon or brush the garlic butter mixture into all the crevices. Make sure to get it deep down between the cuts. Use all the butter mixture.
Step 5: Next, stuff the shredded mozzarella and cheddar cheese blend into every gap and crevice. Be generous and ensure the cheese is distributed evenly throughout the loaf.
Step 6: If using, sprinkle the optional grated Parmesan cheese over the top of the loaf.
Step 7: Loosely wrap the stuffed loaf in aluminum foil and place it on the prepared baking sheet. Bake for 15 minutes.
Step 8: After 15 minutes, remove the foil and continue baking for another 10-15 minutes, or until the cheese is bubbly and melted, and the top of the bread is golden brown and crispy.
Step 9: Remove the pull apart cheesy garlic bread loaf recipe from the oven and let it rest for 5 minutes before serving. This allows the cheese to set slightly, making it easier to pull apart without everything falling out. Garnish with extra fresh parsley if desired and serve warm.