Preheat the oven to the temperature recommended on the garlic bread package.

Bring a large pot of salted water to a boil and cook the spaghetti until just tender (al dente). Drain thoroughly and set aside.

In a large bowl, toss the hot spaghetti with the chosen pasta sauce to absorb the flavor. Stir in any sliced vegetables if using, especially quick-wilting greens like spinach.

Trim the tops off the garlic bread loaves or open the bread bowls and scoop out the soft interior, leaving a sturdy shell. Reserve some crumbs for topping if desired.

Spoon or twirl the sauced spaghetti into each hollowed bread bowl, filling just below the rim to avoid spillover.

Arrange the filled bread bowls on a baking sheet and bake until the bread edges are crisp and the filling is warmed through, about 8 to 12 minutes.

Remove from the oven and sprinkle with grated Parmesan, if desired, and drizzle lightly with olive oil.

Let sit for a minute for the filling to settle, then serve warm.