In a large pot, bring 4 quarts of salted water to a rolling boil. Add spaghetti and cook for 8-10 minutes until al dente. Reserve 1 cup of pasta water and drain.

In a large skillet, heat 2 tablespoons of olive oil over medium heat. Add 4 minced garlic cloves and a pinch of red pepper flakes, sautéing for 1-2 minutes until fragrant.

Add the drained spaghetti to the skillet with the sautéed garlic. Pour in reserved pasta water while tossing the spaghetti to coat evenly for 2-3 minutes.

Remove from heat and stir in 1/4 cup of chopped parsley and 1/2 cup of grated Parmesan. Season with black pepper to taste.

In a small bowl, mix 1/4 cup of softened butter with 2 minced garlic cloves, 2 tablespoons of chopped parsley, and 1/4 cup of Parmesan until smooth.

Slice the Italian bread lengthwise and spread the garlic butter mixture onto both halves.

Preheat the oven to 375°F (190°C) and bake the garlic bread for 10-12 minutes until golden brown. Optionally broil for an additional 1-2 minutes.

Allow the garlic bread to cool slightly, slice, and serve alongside spaghetti, topped with extra Parmesan and parsley.