Start by bringing a large pot of water to a rolling boil over high heat. Add a generous amount of salt to the water, then carefully add the spaghetti. Cook according to package instructions, typically about 8-10 minutes for al dente. Reserve 1 cup of the pasta water for later use and drain the spaghetti in a colander.

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

Add the drained spaghetti into the skillet with the sautéed garlic oil. Toss together, adding reserved pasta water as needed for desired consistency. Stir in chopped parsley and grated Parmesan cheese, seasoning to taste.

In a mixing bowl, combine softened butter, minced garlic, chopped parsley, and Parmesan cheese. Mix until smooth.

Slice the Italian bread lengthwise on a baking sheet, cut sides up. Generously spread the garlic butter mixture over the cut sides.

Preheat your oven to 375°F (190°C). Once hot, place the baking sheet inside and bake for 10-12 minutes until golden brown. Broil for 1-2 minutes if desired.

Serve the spaghetti alongside warm garlic bread slices, garnished with remaining Parmesan cheese and fresh parsley.