Bring a large pot of salted water to a boil. Add the spaghetti and cook until al dente, about 8-10. Drain and reserve 1/2 cup of pasta water.
In a large skillet, melt the butter over medium heat. Add minced garlic and red pepper flakes, cooking for 1-2 until fragrant.
Add the drained spaghetti to the skillet, tossing to coat. Add reserved pasta water as needed. Season with salt, pepper, Parmesan, and parsley.
Preheat oven to 375°F. Slice French bread in half lengthwise. Mix softened butter, garlic powder, and oregano. Spread on bread and top with mozzarella.
Place bread on a baking sheet and bake for 10-12 until cheese is melted and bubbly.