Preheat your oven to 375°F.

Cut the tops off the Italian bread loaves and hollow out the insides, leaving about a 1-inch thick shell. Set aside the bread insides for later use.

Cook the spaghetti according to package instructions until al dente. Drain and set aside.

In a large skillet, heat the olive oil over medium heat. Add the minced garlic and red pepper flakes (if using), and sauté for about 1 minute until fragrant.

Add the cooked spaghetti to the skillet, along with the salt, black pepper, and half of the Parmesan cheese. Toss to combine and heat through for about 2-3 minutes.

Spoon the spaghetti mixture into the hollowed-out bread bowls, packing it in gently.

Sprinkle the remaining Parmesan cheese on top of the filled bread bowls.

Place the filled bread bowls on a baking sheet and bake in the preheated oven for 15-20 minutes, or until the bread is crispy and the cheese is melted.

Remove from the oven and garnish with chopped parsley. Serve with marinara sauce on the side for dipping.