Preheat the Oven: Preheat your oven to 400°F (200°C). Line a large baking sheet with parchment paper or aluminum foil for easy cleanup.
Make the Garlic Butter: In a small mixing bowl, combine the softened salted butter, minced fresh garlic, garlic powder, and chopped parsley. Mash together with a fork until the ingredients are completely blended and smooth.
Prep the Bread: Lay the 8 slices of thick-cut bread flat on your prepared baking sheet in a single layer.
Butter the Slices: Using a knife or offset spatula, spread a generous, even layer of the garlic butter mixture across the top of each slice, making sure to spread it all the way to the edges to prevent the crusts from burning.
Add the Cheese: In a separate bowl, toss the grated mozzarella and cheddar (or parmesan) together. Sprinkle a heavy layer of the cheese mixture over the buttered slices. Gently press the cheese down so it adheres to the butter.
Bake: Place the baking sheet on the middle rack of your preheated oven. Bake for 8 to 10 minutes, or until the cheese is completely melted and the edges of the bread are crispy.
Broil for Color (Optional): For a blistered, golden-brown cheese topping, turn your oven to the Broil setting. Broil for 1 to 2 minutes, watching very closely so the toast does not burn.
Serve: Remove from the oven and let cool for just a minute or two. Serve warm and enjoy the perfect cheese pull!