Bring 4 quarts of water to a rolling boil in a large pot. Add 2 tablespoons of salt and then add the spaghetti. Cook for 8 to 10 minutes until al dente, then reserve 1 cup of pasta water and drain.

In a large skillet, heat 3 tablespoons of olive oil over medium heat. Add 3 cloves of minced garlic and 1 teaspoon of red pepper flakes. Sauté for 1-2 minutes until fragrant.

Add the drained spaghetti to the skillet with the garlic oil. Toss gently and pour in reserved pasta water as needed to achieve a silky sauce.

Stir in ¼ cup of chopped parsley and ½ cup of grated Parmesan cheese. Season with salt and freshly ground black pepper. Toss to combine.

Mix ½ cup of softened unsalted butter, 2 cloves of minced garlic, ¼ cup of chopped parsley, and ¼ cup of grated Parmesan cheese in a separate bowl for the garlic butter.

Slice the Italian bread lengthwise and place it cut side up on a baking sheet.

Spread the garlic butter mixture generously over both halves of the sliced bread.

Preheat oven to 375°F (190°C). Bake the bread for 10-12 minutes until golden brown and bubbly.

Switch to broil and broil for an additional 1-2 minutes for a crispy crust, watching closely to prevent burning.

Remove from the oven, let cool slightly, slice, and serve with spaghetti.